Unlike the GPCR-based vision, smell and tastes, the molecular mechanisms of hearing, touch, and blood-pressure or systemic-osmolarity sensing are unknown. How ion channels receive mechanical forces remain obscure, except for bacterial channels MscL, MscS. We are using the rat TRP channel V4 subtype, to help fill this knowledge gap. Against expectation, we have now shown TRPV4's direct and instant response to membrane stretch under Xenopus oocyte patch clamp. We have also developed yeast as a new arena to dissect TRPV4. Our work is challenging the dominant TRPV4's osmotic- gating model. We plan to define the force-sensing domain within TRPV4, using strategic peptide insertions, truncations and chimeras. We will also test the force-from-lipid theory by examining the effects of membrane-intercalating compounds and by mutating putative lipid-anchoring amino acids. 2008-10 found TRPV4 gain-of-function (GOF) mutations to cause human bone-development pathologies (brachyolmia, metatropic dysplasia, etc.). To characterize and understand the molecular defects caused by these disease alleles, we will elucidate TRPV4's additional gating mechanisms, and will examine all seven human GOF alleles in molecular detail with improved electrophysiological techniques and yeast-based phenotyping.

Public Health Relevance

Ion-channel mechanosensitivity underlies the physiology and pathology of hearing, touch, the sensing of blood pressure, systemic osmolarity etc. Understanding how a channel protein receives forces is fundamental. The molecular functioning of the mechanosensitive TRPV4 channel has direct impact on human health: TRPV4 mutations cause autosomal dominant brachyolmia, spondylmetaphyseal dysplasias Kozlowski type, metatropic dysplasia, scapuloperoneal spinal muscular atrophies, and Charcot- Marie-Tooth disease type 2C in human.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Neurotransporters, Receptors, and Calcium Signaling Study Section (NTRC)
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Nie, Zhongzhen
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University of Wisconsin Madison
Schools of Earth Sciences/Natur
United States
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Teng, Jinfeng; Loukin, Stephen H; Anishkin, Andriy et al. (2016) A competing hydrophobic tug on L596 to the membrane core unlatches S4-S5 linker elbow from TRP helix and allows TRPV4 channel to open. Proc Natl Acad Sci U S A 113:11847-11852
Teng, Jinfeng; Loukin, Stephen; Anishkin, Andriy et al. (2015) The force-from-lipid (FFL) principle of mechanosensitivity, at large and in elements. Pflugers Arch 467:27-37
Loukin, Stephen H; Teng, Jinfeng; Kung, Ching (2015) A channelopathy mechanism revealed by direct calmodulin activation of TrpV4. Proc Natl Acad Sci U S A 112:9400-5
Teng, Jinfeng; Loukin, Stephen H; Anishkin, Andriy et al. (2015) L596-W733 bond between the start of the S4-S5 linker and the TRP box stabilizes the closed state of TRPV4 channel. Proc Natl Acad Sci U S A 112:3386-91
Anishkin, Andriy; Loukin, Stephen H; Teng, Jinfeng et al. (2014) Feeling the hidden mechanical forces in lipid bilayer is an original sense. Proc Natl Acad Sci U S A 111:7898-905
Teng, Jinfeng; Loukin, Steve; Kung, Ching (2014) Mechanosensitive Ion Channels in Cardiovascular Physiology. Exp Clin Cardiol 20:6550-6560
Teng, Jinfeng; Loukin, Stephen; Zhou, Xinliang et al. (2013) Yeast luminometric and Xenopus oocyte electrophysiological examinations of the molecular mechanosensitivity of TRPV4. J Vis Exp :
Anishkin, Andriy; Kung, Ching (2013) Stiffened lipid platforms at molecular force foci. Proc Natl Acad Sci U S A 110:4886-92