Mast cells are pluripotent effector cells that reside in tissue. They respond to diverse stimuli by releasing potent biological mediators into the surrounding tissue. These mediators include extracellular proteases, histamine and serotonin, as well numerous cytokines, chemokines, and growth factors. Immunologically, mast cells play a crucial role in the generation and maintenance of inflammation, in response to antigenic challenge. In addition to responses to immunological stimulation, mast cells also respond to polybasic secretagogues and physical stimuli. Through responsiveness to physical stimuli (thermal, osmotic and mechanical inputs), mast cells contribute to both tissue homeostasis, and the wounding process that follows noxious insults. Each mechanism for mast cell activation relies on calcium influx through specific plasma membrane cation channels. Here, we report that calcium-permeant cation channels of the TRPV family are expressed in mast cells. TRPV ion channels are a newly recognized family of sensors, which receive, and react to, physical environmental cues, including thermal, osmotic and mechanical stimuli. The central premise of the current proposal is that TRPV channels transduce physiological, and pathophysiological, signals that are functionally coupled to calcium signaling and mediator release in mast cells. We propose to study the regulation, and function, of TRPV cation channels in the mast cell context. Our first Specific Aim tests the hypothesis that expression of TRPV2 confers a specific, thermally-evoked, cation conductance upon mast cells. In the second Specific Aim, we will explore a novel regulatory mechanism for TRPV2. Our preliminary data show that TRPV2 is a target for phosphorylation by protein kinase A in mast cells, and that this interaction is mediated by a novel adapter protein, PAP7. PAP7 specifically bridges TRPV2 and PKA. We will explore the functional consequences and upstream regulatory mechanisms for phosphorylation of TRPV2 by PKA, and the contribution of PAP7.
In Specific Aim 3, we will examine the representation and functionality of TRPV channels in dermal mast cells, exploring the hypothesis that TRPVs couple mast cell responses to environmental stimuli in the skin.
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