Formation of a physiological complex between TRPV2 and RGA protein promotes cell surface expression of TRPV2

Abstract

The transient receptor potential, sub-family Vanilloid (TRPV)(2) cation channel is activated in response to extreme temperature elevations in sensory neurons. However, TRPV2 is widely expressed in tissues with no sensory function, including cells of the immune system. Regulation of GRC, the murine homolog of TRPV2 has been studied in insulinoma cells and myocytes. GRC is activated in response to certain growth factors and neuropeptides, via a mechanism that involves regulated access of the channel to the plasma membrane. This is likely to be an important primary control mechanism for TRPV2 outside the CNS. Here, we report that a regulated trafficking step controls the access of TRPV2 to the cell surface in mast cells. In mast cells, elevations in cytosolic cAMP are sufficient to drive plasma membrane localization of TRPV2. We have previously proposed that the recombinase gene activator protein (RGA), a four-transmembrane domain, intracellular protein, associates with TRPV2 during the biosynthesis and early trafficking of the channel. We use a polyclonal antibody to RGA to confirm the formation of a physiological complex between RGA and TRPV2. Finally, we show that over-expression of the RGA protein potentiates the basal surface localization of TRPV2. We propose that trafficking and activation mechanisms intersect for TRPV2, and that cAMP mobilizing stimuli may regulate TRPV2 localization in non-sensory cells. RGA participates in the control of TRPV2 surface levels, and co-expression of RGA may be a key component of experimental systems that seek to study TRPV2 physiology.

The Bacterial Pathogen Xanthomonas oryzae Overcomes Rice Defenses by Regulating Host Copper Redistribution

“…For example, coexpression of fission yeast SpCtr4 and SpCtr5 is required for complementation of S. cerevisiae ctr mutant or S. pombe ctr mutant because the two proteins are interdependent for trafficking to the plasma membrane and form a heteromeric complex for mediating a highaffinity Cu transport; S. pombe Ctr5 is also required for Ctr4 folding (Zhou and Thiele, 2001;Beaudoin et al, 2006). The rat plasma membrane-localized ion channel protein TRPV2 interacts with the endoplasmic reticulum/Golgi apparatus-localized RGA protein; RGA plays role in trafficking of TRPV2 to plasma membrane (Barnhill et al, 2004;Stokes et al, 2005). The RGA is suggested to have four transmembrane regions and is distantly related to the MtN3/saliva-type proteins (Stokes et al, 2005).…”

PI3-kinase promotes TRPV2 activity independently of channel translocation to the plasma membrane

“…In addition, a TRPV2 partner called RGA, has recently been identified by an interaction trap screening. Interaction of RGA with TRPV2 promotes its surface expression, in a protein kinase A dependent way [9]. This suggests that other intracellular pathways might regulate surface expression of TRPV2 channels.…”

“…Although TRPV1, 3 and 4 channels act unambiguously as cellular temperature sensors, the gating of endogenous TRPV2 by noxious heat is still a matter of debate. If TRPV2 is expressed in large diameter dorsal root ganglion neurons that also express capsaicin-insensitive heat activated channels [8], it is also present in numerous other tissues, especially in immune cells [9] where a primary physiological role as thermal sensor remains questionable. In non-neuronal cell lines such as pancreatic MIN6 or CHO cells, it has been proposed that TRPV2 channel activity might be regulated by growth factor signaling [10].…”

Crystal structure of the N-terminal ankyrin repeat domain of TRPV3 reveals unique conformation of finger 3 loop critical for channel function

“…In the TRPV subfamily, all the six members share conserved ankyrin repeat domains (ARDs) in their N-termini. These ankyrin repeats are involved in proteinprotein interactions (Stokes et al, 2005;Kim et al, 2006), channel assembly (Chang et al, 2004;Erler et al, 2004), and traffi cking (Arniges et al, 2006). Visualizing the ARDs of TRPV channels is critical for understanding their molecular basis of channel function and regulatory mechanisms.…”