Modulating the Mechanical Activation of TRPV4 at the Cell-Substrate Interface

Abstract

Ion channels activated by mechanical inputs are important force sensing molecules in a wide array of mammalian cells and tissues. The transient receptor potential channel, TRPV4, is a polymodal, nonselective cation channel that can be activated by mechanical inputs but only if stimuli are applied directly at the interface between cells and their substrate, making this molecule a context-dependent force sensor. However, it remains unclear how TRPV4 is activated by mechanical inputs at the cell-substrate interface, which cell intrinsic and cell extrinsic parameters might modulate the mechanical activation of the channel and how mechanical activation differs from TRPV4 gating in response to other stimuli. Here we investigated the impact of substrate mechanics and cytoskeletal components on mechanically evoked TRPV4 currents and addressed how point mutations associated with TRPV4 phosphorylation and arthropathy influence mechanical activation of the channel. Our findings reveal distinct regulatory modulation of TRPV4 from the mechanically activated ion channel PIEZO1, suggesting the mechanosensitivity of these two channels is tuned in response to different parameters. Moreover, our data demonstrate that the effect of point mutations in TRPV4 on channel activation are profoundly dependent on the gating stimulus.

From stretch to deflection: the importance of context in the activation of mammalian, mechanically activated ion channels

“…The limitation of this technique is that it is solely applicable to dissociated, adherent cells, given that a cell-substrate interaction is required to allow propagation of the mechanical stimulus from the deflected pilus to the molecular force-sensor. Pillar array analysis has proven useful to study how MA channels can be activated and tuned within an intact cell-substrate interface [24,29,[31][32][33][34][35]. In addition, molecular-scale deflections are sufficient to activate MA channels in the most sensitive cells probed thus far (for instance low threshold mechanoreceptive DRG neurons).…”

Diverse Roles of TRPV4 in Macrophages: A Need for Unbiased Profiling

“…TRPV4 was first identified as an osmosensitive channel due to its activation by hypotonicity ( 23 , 24 ). It has since been shown to function as a polymodal non-selective cation channel that can be activated by a diverse array of stimuli including mechanical stress ( 25 – 28 ), warm temperature (above 27°C) ( 29 , 30 ), endogenous polyunsaturated fatty acids (PUFAs) ( 31 – 33 ) and receptor-operated signaling ( 34 ). TRPV4 integrates cellular responses to these various stimuli, enabling this channel to influence a broad range of signaling and associated transcriptional events ( 11 – 14 , 35 – 52 ), as summarized in Figure 1 , and previously reviewed in detail ( 53 ).…”

“…TRPV4 is activated by hypoosmolarity, shear stress or direct deflection at cell-substrate contact points. Activation of TRPV4 by cellular indentation or membrane stretch is also commonly reported ( 25 , 54 ), although the relative importance and generality of this mode of gating has recently been questioned based on electrophysiological studies ( 27 , 28 ). This suggests that TRPV4 may only respond directly to specific mechanical cues.…”

TRPing on Cell Swelling - TRPV4 Senses It

“…Various experimental strategies have been employed to distinguish the two, i.e. stretching of the cell membrane in the absence of a volume change ( 46 – 48 ) which has been employed to demonstrate ( 49 – 51 ) or not to demonstrate ( 9 , 52 , 53 ) direct activation of TRPV4 by mechanical probing. It therefore remains unresolved to what extent TRPV4 activation occurs by direct mechanical probing, rather than as a consequence of the cell volume changes.…”