Actin filament disruption inhibits L-type Ca²⁺ channel current in cultured vascular smooth muscle cells

Abstract

To clarify interactions between the cytoskeleton and activity of L-type Ca(2+) (Ca(L)) channels in vascular smooth muscle (VSM) cells, we investigated the effect of disruption of actin filaments and microtubules on the L-type Ca(2+) current [I(Ba(L))] of cultured VSM cells (A7r5 cell line) using whole cell voltage clamp. The cells were exposed to each disrupter for 1 h and then examined electrophysiologically and morphologically. Results of immunostaining using anti-alpha-actin and anti-alpha-tubulin antibodies showed that colchicine disrupted both actin filaments and microtubules, cytochalasin D disrupted only actin filaments, and nocodazole disrupted only microtubules. I(Ba(L)) was greatly reduced in cells that were exposed to colchicine or cytochalasin D but not to nocodazole. Colchicine even inhibited I(Ba(L)) by about 40% when the actin filaments were stabilized by phalloidin or when the cells were treated with phalloidin plus taxol to stabilize both cytoskeletal components. These results suggest that colchicine must also cause some inhibition of I(Ba(L)) due to another unknown mechanism, e.g., a direct block of Ca(L) channels. In summary, actin filament disruption of VSM cells inhibits Ca(L) channel activity, whereas disrupting the microtubules does not.

T-type current modulation by the actin-binding protein Kelch-like 1

“…Overall this information and the fact that KLHL1 directly interacts with actin confirm that the cytoskeleton plays an important role in the modulation of ␣ 1H , as described for other ion channels (9,16,26,28,35,43). Coimmunoprecipitation experiments of ␣ 1H with actin as bait were unsuccessful in our hands, likely because these experiments did not favor the presence of polymerized actin.…”

Intact Actin Filaments Are Required for Cytosolic Phospholipase A2Translocation but Not for Its Activation by Norepinephrine in Vascular Smooth Muscle Cells

“…Therefore, it is possible that CD and LA block cPLA 2 translocation to the nuclear envelope by interfering with the influx of extracellular Ca 2ϩ . CD has been reported to inhibit voltage activated L-type Ca 2ϩ current in A7r5 vascular smooth muscle cell line (Nakamura et al, 2000). However, in the present study, it seems to be unlikely because neither CD nor LA decreased NE-induced rise in cytosolic Ca 2ϩ in VSMCs.…”

Comparison of cellular effects of starch-coated SPIONs and poly(lactic-co-glycolic acid) matrix nanoparticles on human monocytes

“…25,55,56 As the actin cytoskeleton is important for the functionality and regulation 61 of ion channels via the connection by proteins like cortactin, 19 disruption can modulate the activity of different channels. 24,62,63 Such an effect was, however, not observed in our patch clamp experiments with the MM6 cells. One explanation may be that expression and regulation of ion channels is so complex that the cell alters its expression pattern to maintain a working condition 64 even with a disrupted actin cytoskeleton.…”