HomeCannabis MedicineIn situ visualization of opioid and cannabinoid drug effects using phosphosite-specific GPCR antibodies

In situ visualization of opioid and cannabinoid drug effects using phosphosite-specific GPCR antibodies

April 20, 2023

Commun Biol. 2023 Apr 15;6(1):419. doi: 10.1038/s42003-023-04786-2.

ABSTRACT

G protein-coupled receptors (GPCRs) are important signal transducers that are phosphorylated upon activation at intracellular serine and threonine residues. Although antibodies that specifically recognize the phosphorylation state of GPCRs have been available for many years, efficient immunolocalization of phosphorylated receptors in their tissues of origin has not been possible. Here, we show that phosphorylation of receptors is highly unstable during routine immunohistochemical procedures, requiring the use of appropriate phosphatase inhibitors particular during tissue perfusion, post-fixation, and cryoprotection but not during immunostaining of tissue sections. We provide proof of concept using phosphorylation state-specific μ-opioid receptor (MOP) and cannabinoid receptor 1 (CB1) antibodies. Indeed, three of four well-characterized phosphosite-specific MOP antibodies, including pS375-MOP, pT376-MOP, and pT379-MOP, showed robust neuronal immunostaining in brain and spinal cord sections of opioid-treated mice only after inclusion of phosphatase inhibitors. We then extended this approach to the CB1 receptor and demonstrated that one of three newly-generated phosphosite-specific CB1 antibodies, namely pS425-CB1, showed striking staining of fibers and varicosities in brain slices from cannabinoid-treated mice. Although subsequent experiments showed that phospho-CB1 immunostaining was less sensitive to phosphatases, we conclude that the use of phosphatase inhibitors should always be considered in the development of immunohistochemical procedures for new phosphosite-specific GPCR antibodies. In summary, we anticipate that this improved protocol will facilitate the widespread use of phosphorylation state-specific antibodies to monitor the activation of endogenous GPCRs under physiological and pharmacological conditions. Our approach may also prove useful to confirm target engagement of GPCR drug candidates in native tissues.

PMID:37061609 | PMC:PMC10105690 | DOI:10.1038/s42003-023-04786-2

Related Posts

About The Author

Patrick Blanchard MD

Meet Dr. Blanchard Dr. Blanchard’s medical practice is an embodiment of Integrative health which brings conventional and complementary approaches together in a coordinated way. Conveniently located in sunny Florida and over the internet with ValiseMD’s secure HIPPA compliant telXmed servers. Since 1994, patients with a wide range of challenging medical problems have achieved optimum health using the best of natural medicine, judiciously combined with high-tech innovations. Breakthroughs are often achieved even after patients have consulted mainstream specialists and holistic practitioners. Dr. Blanchard is founder and CEO of ValiseMD, Inc. He is board certified in Family Medicine since 1994 and awarded Fellow of the American Academy of Family Physicians in 2001. He received the ‘Teacher of the Year’ award from the University of Kansas School of Medicine at completion of his residency in Family Medicine. He completed a fellowship at Wake Forest University in the field of vascular neurosonology. He holds a medical patent in the field of Gastroenterology. He holds an unrestricted license to practice medicine and surgery in Florida. He started his medical career as a Emergency Medical Technician, then as a Paramedic and later a Medical Doctor.