Acute inhibition of transient receptor potential vanilloid‐type 4 cation channel halts cytoskeletal dynamism in microglia

Abstract

Microglia, the resident macrophages of the central nervous system, are highly motile cells that support brain development, provision neuronal signaling, and protect brain cells against damage. Proper microglial functioning requires constant cell movement and morphological changes. Interestingly, the transient receptor potential vanilloid 4 (TRPV4) channel, a calcium-permeable channel, is involved in hypoosmotic morphological changes of retinal microglia and regulates temperature-dependent movement of microglial cells both in vitro and in vivo. Despite the broad functions of TRPV4 and the recent findings stating a role for TRPV4 in microglial movement, little is known about how TRPV4 modulates cytoskeletal remodeling to promote changes of microglial motility. Here we show that acute inhibition of TRPV4, but not its constitutive absence in the Trpv4 KO cells, affects the morphology and motility of microglia in vitro. Using high-end confocal imaging techniques, we show a decrease in actinrich filopodia and tubulin dynamics upon acute inhibition of TRPV4 in vitro. Furthermore, using acute brain slices we demonstrate that Trpv4 knockout microglia display lower ramification complexity, slower process extension speed and consequently smaller surveyed area. We conclude that TRPV4 inhibition triggers a shift in cytoskeleton remodeling of microglia influencing their migration and morphology.

Movers and shakers: Microglial dynamics and modulation of neural networks

“…Given that the resting potential is above the equilibrium potential for K + , there are likely other ion channels that contribute to the microglial resting potential, such as TRPV1 (Izquierdo et al, 2019; Marrone et al, 2017) or TRPV4 channels (Nishimoto et al, 2021). Deletion of the temperature‐sensitive Ca 2+ ‐permeable TRPV4 reduces microglial process motility, possibly because of decreased basal Ca 2+ signaling (Beeken et al, 2022; Nishimoto et al, 2021). Additionally, KCa3.1 and Kv1.3 are selectively expressed in microglia and could contribute to their physiology as they modulate microglial responses to ischemic injury (Chen et al, 2011; Chen et al, 2016; Fomina et al, 2021).…”

p27kip1 Modulates the Morphology and Phagocytic Activity of Microglia

“…Microglial morphology was assessed by Sholl analysis, as originally described by Sholl and according to previous research [ 44 , 45 , 87 , 88 ]. Briefly, cell reconstructions were performed using 3D automatic cell tracing in Vaa3D software ( , accessed on 1 February 2021).…”

“…The study of microglial dynamics in acute adolescent brain slices using two-photon imaging was performed according to previous research [ 88 ]. P21 brains were dissected and incubated into ice-cold slicing solution containing (in mM): 120 N-methyl-D-glucamine, 2.5 KCL, 25 NaHCO 3 , 1 CaCl 2 , 7 MgCl 2 , 1.2 NaH 2 PO 4 , 20 D-glucose, 2.4 Na + pyruvate, 1.3 Na + -L-ascorbate, pH 7.3–7.4, ~300 mOsm, which was constantly perfused with 95% O 2 and 5% CO 2 .…”

Astrocytic TRPV4 Channels and Their Role in Brain Ischemia

“…Additionally, microglia with acute inhibition of TRPV4 channels show changes in morphology. However, when TRPV4 is knocked out, the changes do not occur [ 91 ].…”