Tag Archives: #receptor

Newly Discovered Receptor Helps to Sneak a Peek at Evolution (Biology)

What mammals and yeasts can do, plants can do, too: inserting proteins into membranes via a specific pathway. A legacy of their last common ancestor.

Certain proteins call for unusual ways to get incorporated into membranes, because the signal sequence required for this process is located at their rear end instead of at the front. The relevant mechanism and its components are well-known and well-studied in yeast and mammals. Scientists have already hypothesised that it also occurs in plants, but there was no evidence of an indispensable receptor, until now. Existence of the receptor was now proven experimentally by the team headed by Professor Christopher Grefen from the Chair of Molecular and Cellular Botany at Ruhr-Universität Bochum (RUB). The researchers published their report on the 5. January 2021 in the journal Proceedings of the National Academy of Sciences PNAS.

Dietmar Mehlhorn and Christopher Grefen (back) are on the trail of the previously undiscovered receptor. © RUB, Marquard

GET pathway for specific proteins

Together with lipids, membrane proteins are a central component of all biological membranes and fulfil important functions in transport and information transfer within and between cells. The majority of membrane proteins are recognised by a signal recognition particle on the basis of signal sequences at the front end of the protein and are incorporated into the membrane of the endoplasmic reticulum during their synthesis. From there, the proteins are transported to most of the important cellular membranes.

However, there is a functionally important family of membrane proteins whose signal sequence is located at the end of the protein. “Therefore, these proteins can’t be integrated into the membrane the usual way,” explains lead author Lisa Yasmin Asseck. These so-called tail-anchored (TA) proteins use a mechanism known as GET pathway. GET stands for Guided Entry of TA proteins.

Transport and insertion

The central component of the pathway is a vehicle within the cell fluid, the cytosolic ATPase GET3. It transfers the newly synthesized TA proteins to the receptors GET1 and GET2, which are bound to the endoplasmic reticulum and ensure their membrane insertion.

While the pathway with all its components has been thoroughly described in mammals and their more closely related yeasts, it remained puzzling in plants. “Some components could be identified in plants based on sequence similarities, but there was no trace of the receptor protein GET2,” says Christopher Grefen.

An ancient legacy

His team has now successfully identified this previously undiscovered receptor in the model plant Arabidopsis thaliana. By specifically eliminating the receptor – using for example the Crispr/Cas9 genetic scissors – the researchers were also able to study its function more closely. “The only difference between wildtype and Arabidopsis mutants lacking the GET2 receptor is that the latter develop shorter root hairs,” explains Grefen. “This does not restrict the growth of the plants under laboratory conditions, it could, however, pose a problem in the wild – especially when water is scarce.” Interestingly, mammals without a GET2 receptor are unable to survive, whereas yeast cells can grow, since they have developed a backup mechanism that kicks in when the receptor is missing.

A remarkable observation for the researchers is the fact that the GET2 receptors of different organisms show great structural similarities despite differences in sequence. “This suggests that their function is evolutionarily conserved. That means that the GET pathway has been around for a very long time, and today’s organisms have inherited it from their last common ancestor during evolution,” elaborates Christopher Grefen. “The discovery of the protein sequence of GET2 from Arabidopsis provides an important piece of the puzzle for understanding the cross-kingdom evolution of the GET pathway and, at the same time, serves as basis for further studies in other plant and algal species.”

The research was funded by a PhD scholarship of the Carl Zeiss Foundation as well as by the German Research Foundation within the Collaborative Research Centres 1190 and 1101 and the Emmy Noether Programme, funding codes GR 4251/1-1 and 1-2.

Reference: Lisa Yasmin Asseck, Dietmar Gerald Mehlhorn, Jhon Rivera Monroy, Martiniano Maria Ricardi, Holger Breuninger, Niklas Wallmeroth, Kenneth Wayne Berendzen, Minou Nowrousian, Shuping Xing, Blanche Schwappach, Martin Bayer, Christopher Grefen: ER membrane receptors of the GET pathway are conserved throughout eukaryotes, in: PNAS, 2020, DOI: 10.1073/pnas.2017636118 https://www.pnas.org/content/118/1/e2017636118

Provided by RUHR- University Bocham

Molecular Switch Controls Ability to Repair Hearing Loss in Mice (Neuroscience)

In a study in mice, Johns Hopkins Medicine researchers have found a molecular switch that turns off the animal’s ability to repair damaged cells in the inner ear. The findings shed light on regenerative abilities that are present in many species of birds and fish, but get turned off in mammals, including humans.

Photomicrograph showing a cross section of the wall of a mouse cochlea, a bony structure within the inner ear. The hair cells on top capture sound waves. In a new study, Johns Hopkins Medicine researchers found that a molecular “switch” within the supporting cells seen at the bottom of the photo may be able to turn on and off the ability to repair damaged hair cells. Credit: Division of Neurology, Johns Hopkins Medicine

The study was published Sept. 8, 2020, in The Proceedings of the National Academy of Sciences.

“We might have for the first time identified something that explains why humans lost the ability to repair cells related to hearing loss,” says Angelika Doetzlhofer, Ph.D., associate professor of neuroscience at the Johns Hopkins University School of Medicine, and co-author of the study.

More than 37 million adults in the United States report hearing loss. In the majority of cases, it results from damage to sound receptor cells deep within the human ear known as hair cells. These cells line the spiral-shaped walls of the cochlea, a bony structure in the inner ear, and capture sound waves reverberating in the area. Then, they convert the vibrations into electrical impulses that are carried to the brain by nerves.

Hair cells are kept healthy by a layer of cells called supporting cells. In birds and fish, supporting cells can function as progenitors to replace lost hair cells. Recent studies of mammals have shown that supporting cells have some regenerative potential early in life, before the animals start hearing. For example, supporting cells in mouse pups are able to create new hair cells at birth. However, the ability to repair or replace them stops within a week. At that point, any damage done to the hair cells is irreversible.

Based on these data from previous mouse studies, Doetzlhofer and study co-author Xiaojun Li, Ph.D., a postdoctoral fellow in her laboratory, looked to the rodents as a way to better understand what controls the decline in regenerative ability in mammals.

The researchers achieved this by following the levels of a protein and micro RNA in mice, called LIN28B and let-7, respectively. LIN28B and let-7 are what scientists call “mutual agonists,”‘ meaning they control each other’s function within the cell.

They found that when let-7 levels ramp up, LIN28B levels drop at the same time, turning off the mouse’s regenerative ability.

The two researchers found that without LIN28B, hair cell regeneration does not occur. They tested this by using cochlear tissue and cells from genetically engineered mice that enabled the protein and its agonistic RNA to be turned on and off as needed.

The researchers say that their findings suggest LIN28B is the deciding factor as to whether or not the hair cells retain their regenerative abilities. LIN28B, they believe, promotes the regenerative process by turning on progenitor-specific genes in supporting cells, which then reprograms supporting cells into hair cell progenitor-like bodies.

“The most exciting part was seeing the dramatic effects of manipulating these factors. We began the experiment hoping to get any type of response, and to see a restoration regeneration capability was really thrilling,” says Doetzlhofer.

The researchers say that a better understanding of the biology behind hair cell regeneration may lead to the development of future treatments for hearing loss.

References: Xiao-Jun Li, Angelika Doetzlhofer, “LIN28B/let-7 control the ability of neonatal murine auditory supporting cells to generate hair cells through mTOR signaling”, Proceedings of the National Academy of Sciences Sep 2020, 117 (36) 22225-22236; DOI: 10.1073/pnas.2000417117 https://www.pnas.org/content/117/36/22225

Provided by Johns Hopkins University

Researchers Reveal Switch Used in Plant Defense Against Animal Attack (Botany)

Decades of pursuit uncovers receptor, the product of an evolutionary arms race for survival, used by plants to sense herbivores.

For decades, scientists have known that plants protect themselves from the devastation of hungry caterpillars and other plant-munching animals through sophisticated response systems, the product of millions of years of evolution.

Researchers have identified the first key biological switch in plants that sounds an alarm following attack by animals such as leaf-munching caterpillars. ©Schmelz Lab, UC San Diego

The biological mechanisms underlying this attack-counter defense paradigm have been vigorously pursued by plant biologists given that such details will help unlock a trove of new strategies for improved plant health. From countering crop pest damage to engineering more robust global food webs, such information is valuable for ensuring sustainable and reliable yields.

Now, researchers at the University of California San Diego and their colleagues have identified the first key biological switch, or receptor, that sounds an alarm in plants specifically when herbivores attack. The discovery is described in the online publication of the Proceedings of the National Academy of Sciences.

Animals such as humans, cows and insects are heterotrophs that derive their energy either directly or indirectly through the consumption of autotrophs, such as photosynthetic plants. This basic foundation shapes biological interactions across planet Earth. More than 30 years ago plant biologists came to understand that plants can sense an attack from herbivorous animals in a way that is distinct from damage caused by hail storms or falling tree branches.

Similar to how human immune defenses counter an attack from viruses, plants have been shown to respond to danger from plant-eating animals through an intricate immune system of receptors. Using a method of pinpointing genetic variants, called forward genetics, research led by Adam Steinbrenner, Alisa Huffaker and Eric Schmelz of UC San Diego’s Division of Biological Sciences enabled discovery the inceptin receptor, termed INR, in bean plants. The receptor detects conserved plant protein fragments accidently released as digestive products during caterpillar munching, thereby enabling plant recognition of attack.

“INR represents the first documented mechanism of a plant cell surface receptor responsible for perceiving animals,” said Schmelz, whose work was accomplished by deconstructing and leveraging the active evolutionary arms race between plants and herbivores. “Our work provides some of the earliest defined mechanistic insights into the question of how plants recognize different attacking herbivores and activate immunity to animals. It is a fundamental question in biology that has been pursued for 30 years.”

Beyond beans, the finding raises interest in using INR, and potentially other receptors that remain to be discovered, as a way to boost defenses in essential agricultural crops.

“A key lesson is that plant perception mechanisms for herbivores can be precisely defined and moved into crops to afford enhanced protection,” said Schmelz. “We have shown one example but it’s clear that hundreds if not thousands of opportunities exist to identify and stack key traits to enhance crop plant immunity to herbivores.”

References: Adam D. Steinbrenner, Maria Muñoz-Amatriaín, Antonio F. Chaparro, Jessica Montserrat Aguilar-Venegas, Sassoum Lo, Satohiro Okuda, Gaetan Glauser, Julien Dongiovanni, Da Shi, Marlo Hall, Daniel Crubaugh, Nicholas Holton, Cyril Zipfel, Ruben Abagyan, Ted C. J. Turlings, Timothy J. Close, Alisa Huffaker, Eric A. Schmelz, “A receptor-like protein mediates plant immune responses to herbivore-associated molecular patterns”, Proceedings of the National Academy of Sciences Nov 2020, 202018415; DOI: 10.1073/pnas.2018415117 https://www.pnas.org/content/early/2020/11/20/2018415117

Provided by University of California – San Deigo

Plants Communicate At A Molecular Level (Botany)

Biologists at FAU identify a protein which recognises Cuscuta as a parasite.

Cuscuta spp., also known as dodder, is a parasitic vine which grafts to the host plant using special suckers to obtain water, minerals and carbohydrates. The parasite also attacks and damages crops such as oilseed rape, sweetcorn, soy, flax or clover. Although the infection generally goes undetected by the host, some species of tomato actively defend themselves by forming wooden tissue which prevents the suckers from penetrating the plant. In earlier research, the biologists at FAU discovered that these tomatoes possess a special receptor, the Cuscuta receptor 1 (CuRe1), which triggers the defence mechanism. However, until now it was unclear how the receptor recognises the danger posed by the dodder.

The researchers have now succeeded in answering this question: the dodder possesses a specific marker in its cellular wall, a glycine-rich protein (GRP). Using its receptor CuRe1, the tomato is able to recognise the molecular pattern of the GRP and identify the dodder as a pathogen, and triggers the immune reaction as a result. The new findings concerning the molecular dialogue between the Cuscuta marker and the tomato receptor may help to increase the resistance of crop plants against parasitic plants.

References: Hegenauer, V., Slaby, P., Körner, M. et al. The tomato receptor CuRe1 senses a cell wall protein to identify Cuscuta as a pathogen. Nat Commun 11, 5299 (2020). https://doi.org/10.1038/s41467-020-19147-4

Provided by UNIVERSITY OF ERLANGEN-NUREMBERG

Skeletal Muscle Development And Regeneration Mechanisms Vary By Gender (Biology)

Researchers at Kumamoto University, Japan generated mice lacking the estrogen receptor beta (ERβ) gene, both fiber-specific and muscle stem cell-specific, which resulted in abnormalities in the growth and regeneration of skeletal muscle in female mice. This was not observed in male mice that lacked the ERβ gene, suggesting that estrogen and its downstream signals may be a female-specific mechanism for muscle growth and regeneration.

• ERβ controls muscle growth in young female mice
• ERβ is essential for muscle regeneration in female mice
• Inactivation of ERβ causes an increase in apoptosis
• ERβ is required for satellite cell population expansion. ©Associate Professor Yusuke Ono.

In humans, skeletal muscle mass generally peaks in the 20s with a gradual decline beginning in the 30s, but it is possible to maintain muscle mass through strength training and a healthy lifestyle. Skeletal muscle can be damaged through excessive exercise or bruising, but it has the ability to regenerate. The muscle stem cells that surround muscle fibers are essential for this regeneration; they also play a part in increasing muscle size (hypertrophy). Muscle stem cell dysfunction is thought to be associated with various muscle weakness, such as age-related sarcopenia and muscular dystrophy. Although basic research on skeletal muscle has progressed rapidly in recent years, most studies were conducted on male animals and gender differences were given much consideration.

Estrogen is a female hormone that maintains the homeostasis of various tissues and organs. A decrease in estrogen levels due to amenorrhea, menopause, or other factors can lead to a disturbance in biological homeostasis. When estrogen binds to estrogen receptors (ERs) in cells, it is transferred into the nucleus and binds to genomic DNA to induce the expression of specific genes as transcription factors. There are two types of ERs, ERα and ERβ. While both ERα and ERβ have high binding capacity to estrogen, their tissue distribution is different, they do not have a common DNA-binding domain, and they may act as antagonists to each other, suggesting that they have different roles. Furthermore, estrogen’s effects on cells can be both ER-mediated and non-ER-mediated.

Increased type I collagen-positive areas indicate fibrosis of muscle tissue. Fibrosis is seen only in female scKO mice.
Left: Muscle stem cells with stained type I collagen (red), laminin (green), and nuclei (blue).
Right: Relative comparison of type I collagen-positive areas. ©Associate Professor Yusuke Ono

An epidemiological study of pre and postmenopausal women in their 50s indicated an association between decreased blood estrogen levels and muscle weakness. A research group at Kumamoto University previously showed that estrogen is important for skeletal muscle development and regeneration using an ovariectomized estrogen deficiency mouse model (Kitajima and Ono, J Endocrinol 2016). They also examined the effectiveness of nutritional interventions in estrogen-deficient conditions (Kitajima et al., Nutrients 2017). However, whether estrogen acts directly on the ER of muscle fibers and muscle stem cells to regulate skeletal muscle growth and regeneration, or whether it acts indirectly through other tissues and organs was unclear. In this study, the researchers generated mice with either myofiber-specific or muscle stem cell-specific ERβ gene deletion and analyzed the function of ERβ in skeletal muscle.

To clarify the role of ERβ in the growth of skeletal muscle, researchers generated mice (mKO) in which the action of the ERβ gene could be turned off in myofibers with the administration of the drug doxycycline. ERβ deficiency was induced at 6 weeks of age, and muscle fiber area and strength of the tibialis anterior muscle was measured at 10-12 weeks. Compared to control mice, both indices were reduced in female mKO mice but not in male mice. Since there was no change in the expression of muscle atrophy-related genes, this reduced growth of female mice was not thought to be due to an increase in muscle atrophy. Ovariectomy-induced estrogen deficiency is known to be associated with muscle quality changes, such as a relative increase in the proportion of fast-type fibers (Kitajima and Ono, J Endocrinol 2016), but no such qualitative changes were observed in mKO mice. It was therefore suggested that, while it may have a direct effect on myofiber growth via ERβ (as expressed in myofibers), estrogen may also regulate the quality of myofibers in a non-ERβ-mediated manner.

(Top) Proliferation of muscle stem cells around an isolated and cultured single muscle fiber.
(Bottom) Increased cell death, decreased expression of Niche-related genes and increased expression of cellular senescence-related genes in scKO mice. ©Associate Professor Yusuke Ono

To determine the function of ERβ in muscle stem cells, the researchers generated scKO mice in which the ERβ gene could be deleted in muscle stem cells with the administration of the drug tamoxifen. They then evaluated muscle regenerative capacity by locally inducing muscle damage. While muscle regeneration was efficient in control mice, the regenerated muscle tissue of female scKO mice showed thin regenerated muscle fibers, fibrosis caused by collagen deposition, and significantly reduced muscle regenerative capacity. Muscle regeneration in male scKO mice, however, was not impaired. Because impaired muscle regeneration in females was not exacerbated by ovariectomies that made them estrogen deficient, the researchers thus thought that estrogen regulates muscle regeneration via ERβ expressed by muscle stem cells.

To further investigate the cause of reduced muscle regenerative capacity, researchers isolated and cultured muscle stem cells for evaluation. ERβ in cells from scKO mice was evaluated in several experiments using siRNAs and inhibitors. ERβ was found to contribute to the promotion of muscle stem cell proliferation and the inhibition of cell death. Gene expression analysis (RNA-seq) of scKO muscle stem cells showed that the expression of “niche”-related genes, which are required for the maintenance of stem cell properties, was reduced in scKO muscle stem cells. Therefore, the researchers hypothesize that the inactivation of ERβ may have affected the proliferation and survival of muscle stem cells by inhibiting the formation of stem cell niches.

This study is thought to be the first to show that ERβ in genetic mouse models plays an important role in the growth and regeneration of skeletal muscle through its function in both muscle fibers and muscle stem cells. However, the role of ERβ in male mice has not yet been elucidated and remains to be addressed even though its expression in both male and female mice is comparable.

“Amenorrhea is induced in female athletes through rigorous training or excessive dieting and has become one of three major problems, together with low energy availability and osteoporosis, faced by female athletes worldwide,” said study leader Associate Professor Yusuke Ono. “Although the animal findings of this study cannot be directly applied to humans, they do suggest that decreased estrogen during amenorrhea may suppress ERβ activity in muscle fibers and muscle stem cells. For female athletes, this may lead to poor athletic performance and delayed recovery from injuries, and puts them at risk for adverse competitive conditions. Our plan is to continue investigating the pathogenesis of age-related sarcopenia and muscular dystrophy by targeting ERβ and its downstream signals with the goal of developing treatments.”

References: Seko, D., Fujita, R., Kitajima, Y., Nakamura, K., Imai, Y., & Ono, Y. (2020). Estrogen Receptor β Controls Muscle Growth and Regeneration in Young Female Mice. Stem Cell Reports. doi: http://dx.doi.org/10.1016/j.stemcr.2020.07.017

Provided by Kumamoto University

Why Drugs Sometimes Cause Receptor Potentiation Rather Than Inhibition? (Neuroscience)

Some highly selective drugs cause unexpected effects in nerve cells: they not only reduce the activation of certain receptors, but also their inactivation.

In order to treat certain brain diseases more precisely and with fewer side effects, researchers are focusing on drugs that only inhibit distinct subtypes of the receptors responding to the neurotransmitter glutamate. However, under certain conditions, such drugs can elicit the opposite effect: Rather than inhibiting the receptors as desired, they potentiate their activity. Professor Andreas Reiner and Stefan Pollok from the junior research group Cellular Neurobiology at Ruhr-Universität Bochum (RUB) report on this unexpected finding and the underlying mechanisms in the journal PNAS from 30 September 2020.

Setup for Patch-Clamp Electrophysiology (IMAGE): Using a dedicated application technique and electrophysiological measurements, the researchers rapidly activated the glutamate receptors. The picture shows a setup for patch-clamp electrophysiology. © RUB, Marquard

Glutamate is the messenger substance, which the brain uses to pass on excitatory signals. Receptors for this neurotransmitter are a promising target for drug development, as they are involved in many pathological processes. For example, they play a role in epilepsy, mental disorders, strokes or brain tumours. “In these cases, it may be beneficial to reduce the activity of glutamate receptors,” explains Andreas Reiner. For this purpose, so-called antagonists have been developed, i.e. drugs that inhibit the activation of glutamate receptors. However, many of these antagonists inhibit all glutamate receptor subtypes, thus producing undesired adverse effects. To circumvent this problem, researchers are currently looking for drugs that only bind to certain receptor subtypes.

Measuring the effects of antagonists directly

In their current study, the researchers analysed the effects of such antagonists on selected receptor subtypes in more detail. For this purpose, they used cultivated cells containing only individual subtypes or specific receptor combinations. Using a dedicated application technique and electrophysiological measurements, the researchers rapidly activated the glutamate receptors, similar to their activation at synapses in the brain, and measured the influence of the antagonists.

Potentiation instead of inhibition

“We made a surprising observation in the process,” says Stefan Pollok. “For certain receptor combinations, we did indeed see a reduction in activation, as expected, but, at the same time, the natural inactivation process was reduced or even completely abolished.” The result was a longer-lasting and overall stronger response than without the antagonist. Instead of the desired inhibition, the researchers observed a potentiating effect.

In subsequent experiments, the team identified the molecular mechanisms of this behaviour more precisely: The potentiating effect is observed when the antagonists bind to receptors that consist of different subunits where it acts on only a part of the subunits. “Such so-called heteromeric receptors are, however, of great importance for signal transduction in the central nervous system,” says Andreas Reiner. The findings are therefore significant for neuroscientists, who are increasingly using selective antagonists to decipher the function of the various receptor subtypes. On the other hand, the study might also have an impact on the development of new therapeutics. “We’ve gained new insights into how this fascinating class of receptors works,” concludes Andreas Reiner. In the future, he also wants to investigate the effects of other glutamate receptor drugs.

References: Stefan Pollok and Andreas Reiner, “Subunit-selective iGluR antagonists can potentiate heteromeric receptor responses by blocking desensitization”, PNAS first published September 30, 2020; https://doi.org/10.1073/pnas.2007471117 link: https://www.pnas.org/content/early/2020/09/29/2007471117

Provided by Ruhr-University Bocham

Researchers Discovered Potential Cause Of Immunotherapy-Related Neurotoxicity (Neuroscience)

New research has uncovered the previously unknown presence of CD19—a B cell molecule targeted by chimeric antigen receptor (CAR) T cell immunotherapy to treat leukemia, lymphoma, and multiple myeloma—in brain cells that protect the blood brain barrier (BBB).

This discovery may potentially be the cause for neurotoxicity in patients undergoing CD19 directed CAR T cell immunotherapy, according to the research team led by Avery Posey, Ph.D., an assistant professor of Systems Pharmacology and Translational Therapeutics in the Perelman School of Medicine at the University of Pennsylvania and Research Health Science Specialist at the Corporal Michael J. Crescenz VA Medical Center in Philadelphia, PA. The study was published today in Cell.

“Our work has revealed that there is CD19 expression in a subset of cells that are, one, not B cells, and two, potentially related to the neurotoxicity we observe in patients treated with CAR T cell therapy targeting CD19,” Posey said. “The next question is, can we identify a better target for eliminating B cell related malignancies other than CD19, or can we engineer around this brain cell expression of CD19 and build a CAR T cell that makes decisions based on the type of cell it encounters—for instance, CAR T cells that kill the B cells they encounter, but spare the CD19 positive brain cells?”

As so often happens in scientific endeavors, the path to this discovery was made somewhat by chance. Kevin Parker, a Ph.D. student at Stanford and co-author on the paper, was at home analyzing previously published single cell sequencing data sets in his spare time. He found CD19 expression in a data set of fetal brain samples that looked odd, because the accepted wisdom was that CD19 only existed in B cells. So his lab reached out to the pioneers of CAR T cell immunotherapy, Penn Medicine.

“I suggested we test this as a preclinical model. When we treated the mouse model with CAR T cells targeting the mouse version of CD19, we found what looks like the start of neurotoxicities,” Posey said.

The team observed an increase in BBB permeability when mouse CD19 was targeted by CAR T cells, even in mice that lack B cells, but not when human CD19 was targeted as a control treatment (mice do not express human CD19).

“Even more interesting, this BBB permeability was more severe when the CAR T cells were fueled by a costimulatory protein called CD28 than when the CAR T cells used 4-1BB,” Posey said “This difference in the severity of BBB permeability correlates with what we know about the clinical observations of CAR T cell-related neurotoxicities—the frequency of patients experiencing high-grade neurotoxicity is lower for those that received the 4-1BB-based CAR T cells.”

His team sought to investigate the higher incidence of neurotoxicity in CD19-directed immunotherapies, compared to treatments targeting other B cell proteins, such as CD20. Notably, CD19 CAR T cells are sensitive to even low levels of CD19 antigen density, emphasizing the importance of identifying any potential reservoir of CD19 other than B cells.

The researchers’ discovery of CD19 molecules in the brain provides evidence that this increase in neurotoxicity is due to CD19-directed CAR T cell immunotherapies. Posey said, though, that generally this neurotoxicity is temporary and patients recover.

This research also highlights the potential utility of developing a comprehensive human single-cell atlas for clinical medicine. Sequencing is an unbiased, genome-wide measurement of gene expression that can capture even rare populations of cells. These rare cell types might otherwise be missed in measurements of bulk tissue due to their low frequency, but as this study demonstrates could be critically important in understanding the clinical effects of targeted therapy. While current CAR T cells recognize only a single antigen, future generations of CAR T cells may be able to discriminate between unique combinations of target antigens to improve thei

r cell-type specificity. The researchers envision that a comprehensive database of gene expression across all human cell types will enable the precise identification of cell type-specific target antigens which can be used to design safe and effective cellular immunotherapies.

“That’s what we think one of the biggest take-home messages is,” Posey said. “The incredible usefulness of single cell atlas or single cell sequencing technology to determine whether a potential immunotherapy or drug target is going to be present somewhere in the body that we would not normally expect it based on conventional thought and whether this expression may lead to toxicity.”

CD19 is thought to be a lineage-restricted molecule—behaving in a functionally and structurally limited way. But this study shows that some small percentage of brain cells also express CD19.

“We would not have identified that through bulk sequencing, where we’re looking at a population of cells versus a single cell type,” Posey said. “It’s only through single cell sequencing that we’re able to identify that there’s this very small percentage of cells in the brain that also contain this molecule, contrary to popular thought.”

References: Kevin R. Parker et al. Single-Cell Analyses Identify Brain Mural Cells Expressing CD19 as Potential Off-Tumor Targets for CAR-T Immunotherapies. Cell. Published: September 21, 2020. DOI:doi.org/10.1016/j.cell.2020.08.022 link: https://www.cell.com/cell/fulltext/S0092-8674(20)31013-8?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0092867420310138%3Fshowall%3Dtrue

We Now Know, How Cannabinoids May Be Useful To Prevent Colon Cancer (Medicine / Oncology)

Inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis are caused by unrestrained inflammation of the gastrointestinal tract. Patients with IBD are at a higher risk of developing colorectal cancer. In a recent study, researchers showed that delta-9-tetrahydrocannabinol (THC), can prevent the development of colitis-associated colon cancer in mice. It was shown that THC suppressed inflammation in the colon, preventing the onset of cancers caused by a carcinogen.

THC preventing the development of colitis-associated colon cancer in mice

Working through cannabinoid receptor 2 (CB2), THC increases CD103 expression on DCs (dendritic cells) and macrophages and upregulates TGF-β1 to increase T regulatory cells (Tregs). THC-induced Tregs are necessary to remedy systemic IFNγ and TNFα caused by anti-CD40, but CB2-mediated suppression of APCs by THC quenches pathogenic release of IL-22 and IL-17A in the colon. By examining tissues from multiple sites, they confirmed that THC affects DCs, especially in mucosal barrier sites in the colon and lungs, to reduce DC CD86. Using models of colitis and systemic inflammation they showed that THC, through CB2, is a potent suppressor of aberrant immune responses by provoking coordination between APCs and Tregs.

Their results showed that THC was acting through CB2 receptors, which is exciting and suggested that compounds that activate CB2 and cause no psychoactive effects may be beneficial to prevent IBD and colon cancer.

References: William Becker et al, Activation of Cannabinoid Receptor 2 Prevents Colitis-Associated Colon Cancer through Myeloid Cell De-activation Upstream of IL-22 Production, iScience (2020). DOI: 10.1016/j.isci.2020.101504 link: https://www.cell.com/iscience/fulltext/S2589-0042(20)30696-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2589004220306969%3Fshowall%3Dtrue