John M Streicher

Interests

Research

I am interested in the molecular mechanisms underlying signal transduction, with a focus on GPCRs and the opioid receptors. By understanding which cascades and transduction mechanisms lead to which aspects of the overall response, both good and bad, we can design drugs which activate only the cascades we want, potentially improving the therapeutic index of new analgesic drugs. In my lab we investigate both sides of this approach, describing new signal transduction mechanisms, and screening experimental drugs for development and eventual human use.

Courses

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Scholarly Contributions

Chapters

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  Heat shock protein 90 (Hsp90) regulates a broad swathe of proteins critical for normal and pathological cell function. One major class of regulated proteins are signal transduction molecules, such as the Mitogen Activated Protein Kinases (MAPK), G Protein Coupled Receptor (GPCR) regulatory kinases, and similar. Hsp90 regulates these signaling proteins by promoting proper folding and protein stability, however, Hsp90 also regulates signaling activation and association/targeting of mature proteins during the course of acute signal transduction. As these signaling proteins are ubiquitously expressed in most cells and are downstream of numerous different receptor systems, Hsp90 regulation of signaling proteins is strongly and broadly impactful. In this chapter, we will discuss the main themes of signaling protein regulation by Hsp90, and highlight several crucial signaling protein families. We will discuss the impact of Hsp90 on signaling downstream of multiple receptor systems, and subsequent effects on physiology and pathophysiology. We will also suggest means to manipulate these regulatory relationships to improve clinical therapy, and future directions for the field of Hsp90 signaling regulation.

Journals/Publications

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  : The role of the molecular chaperone heat shock protein 90 (Hsp90) in pain and analgesia has been recognized; however, no study to date has investigated its role in facial allodynia during headache. In the current study, we examined the role of Hsp90 and its possible connection to the endocannabinoid system utilizing a rodent model of cortical spreading depression (CSD). : CSD, a physiological phenomenon associated with headache disorders, was induced by cortical injection of KCl in female Sprague Dawley rats. To selectively inhibit Hsp90, 17-AAG was applied on the dura mater 24 h before CSD induction. Periorbital allodynia was assessed by von Frey filaments, while tissue samples were subjected to LC-MS, qPCR, Western immunoblotting, and the GTPγS coupling assay. : Increased expression of Hsp90 was selectively observed in the periaqueductal gray (PAG) harvested 90 min after cortical KCl injection, suggesting increased cellular stress from CSD induction. Application of 17-AAG (0.5 nmol) on dura mater 24 h before CSD induction significantly prevented facial allodynia as measured by von Frey filaments. This effect was blocked by injection of the CBR antagonist rimonabant (1 mg/kg, ip). The pretreatment with 17-AAG significantly increased the level of anandamide (AEA) in PAG 90 min after cortical insult, as measured by LC-MS. This effect was accompanied by reduced expression of FAAH and increased expression of NAPE-PLD in the same nuclei. : These results suggest that Hsp90 inhibition positively modulates the endocannabinoid system, causing pain relief through descending pain modulation in PAG post-CSD.

Proceedings Publications

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  Opioid receptors (ORs) are G-protein Coupled Receptors (GPCRs), which mediate analgesia, tolerance, withdrawal, GI transit. Classically, ORs couple inhibitory Gi/o proteins and recruit arrestin – a multifaceted scaffold molecule implicated in opioid mediated effects including tolerance, constipation, dysphoria and naseua [1,2]. Upon activation -arrestin and Gi/o induce downstream signaling responses such as reduced cAMP levels. Recent drug discovery efforts identified several functionally selective exogenous opiates which prefer certain signaling pathways at a given receptor – such as G stimulation – to others – such as -arrestin recruitment and generate desired pharmacological properties [3,4]. Noting that most of the 20+ endogenous opioid peptides are nonselective and some opiates display functional selectivity, two important points emerge. First, endogenous and exogenous ligands, such as those used during studies, do not necessarily generate the same effects. Second, two different endogenous opioid peptides may differentially activate a given receptor. Dynorphin A (DynA) and Dynorphin B (DynB) are considered OR agonists, despite binding to the OR at 1.29nM and 3.39 nM [1], respectively. The Dynorphins start with the 5 amino acid Leuenkephalin (Leu-Enk) sequence – YGGFL – traditionally considered a OR agonist followed by distinct C-terminal sequences. Thus, we ask: Do Dynorphin A (1-17), Dynorphin B (1-13) and Leuenkephalin induce functionally selective signaling at the OR?

Poster Presentations