title: Direct binding of alpha-actinin enhances TRPP3 channel activity.
abstract: Transient receptor potential (TRP) polycystin 2 and 3 (TRPP2 and 3) are homologous members of the TRP superfamily of cation channels but have different physiological functions. TRPP2 is part of a flow sensor, and is defective in autosomal dominant polycystic kidney disease and implicated in left-right asymmetry development. TRPP3 is reported to implicate in sour tasting in bipolar cells of taste buds of the tongue and in the regulation of pH-sensitive action potential in neurons surrounding the central canal of spinal cord. TRPP3 is present in both excitable and non-excitable cells in various tissues, such as retina, brain, heart, testis, and kidney, but its common and cell type-specific functional characteristics remain largely unknown. In this study, we investigated physical and functional interactions between TRPP3 and alpha-actinin, an actin-bundling protein known to regulate several types of ion channels. We employed planer lipid bilayer electrophysiology system to study the function of TRPP3 channel that was affinity-purified from Madin-Darby canine kidney cells. Upon reconstitution in bilayer, TRPP3 exhibited cation channel activities that were substantially augmented by alpha-actinin. The TRPP3-alpha-actinin association was documented by co-immunoprecipitation using native cells and tissues, yeast two-hybrid, and in vitro binding assays. Further, TRPP3 was abundantly present in mouse brain where it associates with alpha-actinin-2. Taken together, alpha-actinin not only attaches TRPP3 to the cytoskeleton but also up-regulates TRPP3 channel function. It remains to be determined whether the TRPP3-alpha-actinin interaction is relevant to acid sensing and other functions in neuronal and non-neuronal cells.
authors.affiliation: Membrane Protein Research Group, Department of Physiology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Dai
authors.forename: Patrick Y
authors.initials: PY
authors.lastname: Shen
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Wu
authors.forename: Wentong
authors.initials: W
authors.lastname: Long
authors.forename: Carl X
authors.initials: CX
authors.lastname: Chen
authors.forename: Zahir
authors.initials: Z
authors.lastname: Hussain
authors.forename: Shaohua
authors.initials: S
authors.lastname: Wang
authors.forename: Xing-Zhen
authors.initials: XZ
authors.lastname: Chen
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000185:Actinin / Q000378:metabolism*; D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism*; D004285:Dogs; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D009475:Neurons, Afferent / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism*; D050396:TRPP Cation Channels / Q000378:metabolism*; D015854:Up-Regulation / Q000502:physiology
chemical_list: D015220:Calcium Channels; C117185:PKD2L1 protein, human; D011956:Receptors, Cell Surface; D050396:TRPP Cation Channels; D000185:Actinin