Mechanosensitive Ca2+ permeant cation channels in human prostate tumor cells

Abstract

The acquisition of cell motility plays a critical role in the spread of prostate cancer (PC), therefore, identifying a sensitive step that regulates PC cell migration should provide a promising target to block PC metastasis. Here, we report that a mechanosensitive Ca2+-permeable cation channel (MscCa) is expressed in the highly migratory/invasive human PC cell line, PC-3 and that inhibition of MscCa by Gd3+ or GsMTx-4 blocks PC-3 cell migration and associated elevations in [Ca2+]i. Genetic suppression or overexpression of specific members of the canonical transient receptor potential Ca2+ channel family (TRPC1 and TRPC3) also inhibit PC-3 cell migration, but they do so by mechanisms other that altering MscCa activity. Although LNCaP cells are nonmigratory, they also express relatively large MscCa currents, indicating that MscCa expression alone cannot confer motility on PC cells. MscCa in both cell lines show similar conductance and ion selectivity and both are functionally coupled via Ca2+ influx to a small Ca2+-activated K+ channel. However, MscCa in PC-3 and LNCaP cell patches show markedly different gating dynamics—while PC-3 cells typically express a sustained, non-inactivating MscCa current, LNCaP cells express a mechanically-fragile, rapidly inactivating MscCa current. Moreover, mechanical forces applied to the patch, can induce an irreversible transition from the transient to the sustained MscCa gating mode. Given that cancer cells experience increasing compressive and shear forces within a growing tumor, a similar shift in channel gating in situ would have significant effects on Ca2+ signaling that may play a role in tumor progression.