Mechanosensitive Ca2 +-permeable channels in human leukemic cells: Pharmacological and molecular evidence for TRPV2

• Membrane stretch activates cation channels in human T cells.
• Stretch-activated channels weakly discriminate between Na+, K+, Mg2 +, and Ca2 +.
• Pharmacological profile suggests that stretch-activated channels are formed by TRPV2.
• Human TRPV2 siRNA virtually abolished stretch-activated current.

Mechanosensitive channels are present in almost every living cell, yet the evidence for their functional presence in T lymphocytes is absent. In this study, by means of the patch-clamp technique in attached and inside-out modes, we have characterized cationic channels, rapidly activated by membrane stretch in Jurkat T lymphoblasts. The half-activation was achieved at a negative pressure of ~ 50 mm Hg. In attached mode, single channel currents displayed an inward rectification and the unitary conductance of ~ 40 pS at zero command voltage. In excised inside-out patches the rectification was transformed to an outward one. Mechanosensitive channels weakly discriminated between mono- and divalent cations (PCa/PNa ~ 1) and were equally permeable for Ca2 + and Mg2 +. Pharmacological analysis showed that the mechanosensitive channels were potently blocked by amiloride (1 mM) and Gd3 + (10 μM) in a voltage-dependent manner. They were also almost completely blocked by ruthenium red (1 μM) and SKF 96365 (250 μM), inhibitors of transient receptor potential vanilloid 2 (TRPV2) channels. At the same time, the channels were insensitive to 2-aminoethoxydiphenyl borate (2-APB, 100 μM) or N-(p-amylcinnamoyl)anthranilic acid (ACA, 50 μM), antagonists of transient receptor potential canonical (TRPC) or transient receptor potential melastatin (TRPM) channels, respectively. Human TRPV2 siRNA virtually abolished the stretch-activated current. TRPV2 are channels with multifaceted functions and regulatory mechanisms, with potentially important roles in the lymphocyte Ca2 + signaling. Implications of their regulation by mechanical stress are discussed in the context of lymphoid cells functions.

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