title: Phosphatidylinositol-4,5-biphosphate-dependent rearrangement of TRPV4 cytosolic tails enables channel activation by physiological stimuli.
abstract: Most transient receptor potential (TRP) channels are regulated by phosphatidylinositol-4,5-biphosphate (PIP2), although the structural rearrangements occurring on PIP2 binding are currently far from clear. Here we report that activation of the TRP vanilloid 4 (TRPV4) channel by hypotonic and heat stimuli requires PIP2 binding to and rearrangement of the cytosolic tails. Neutralization of the positive charges within the sequence (121)KRWRK(125), which resembles a phosphoinositide-binding site, rendered the channel unresponsive to hypotonicity and heat but responsive to 4α-phorbol 12,13-didecanoate, an agonist that binds directly to transmembrane domains. Similar channel response was obtained by depletion of PIP2 from the plasma membrane with translocatable phosphatases in heterologous expression systems or by activation of phospholipase C in native ciliated epithelial cells. PIP2 facilitated TRPV4 activation by the osmotransducing cytosolic messenger 5'-6'-epoxyeicosatrienoic acid and allowed channel activation by heat in inside-out patches. Protease protection assays demonstrated a PIP2-binding site within the N-tail. The proximity of TRPV4 tails, analyzed by fluorescence resonance energy transfer, increased by depleting PIP2 mutations in the phosphoinositide site or by coexpression with protein kinase C and casein kinase substrate in neurons 3 (PACSIN3), a regulatory molecule that binds TRPV4 N-tails and abrogates activation by cell swelling and heat. PACSIN3 lacking the Bin-Amphiphysin-Rvs (F-BAR) domain interacted with TRPV4 without affecting channel activation or tail rearrangement. Thus, mutations weakening the TRPV4-PIP2 interacting site and conditions that deplete PIP2 or restrict access of TRPV4 to PIP2--in the case of PACSIN3--change tail conformation and negatively affect channel activation by hypotonicity and heat.
authors.affiliation: Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Garcia-Elias
authors.forename: Sanela
authors.initials: S
authors.lastname: Mrkonjic
authors.forename: Carlos
authors.initials: C
authors.lastname: Pardo-Pastor
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Inada
authors.forename: Ute A
authors.initials: UA
authors.lastname: Hellmich
authors.forename: Fanny
authors.initials: F
authors.lastname: Rubio-Moscardó
authors.forename: Cristina
authors.initials: C
authors.lastname: Plata
authors.forename: Rachelle
authors.initials: R
authors.lastname: Gaudet
authors.forename: Rubén
authors.initials: R
authors.lastname: Vicente
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Valverde
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000704:Analysis of Variance; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010704:Phorbols / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: C517592:4alpha-phorbol 12,13-didecanone; D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; C421762:PACSIN3 protein, human; D010704:Phorbols; D019269:Phosphatidylinositol 4,5-Diphosphate; D050916:TRPV Cation Channels; C416986:TRPV4 protein, human; D002118:Calcium
keywords: regulation; structure; thermosensitivity