Mechanosensitivity of N-type calcium channel currents.
Mechanosensitivity in voltage-gated calcium channels could be an asset to calcium signaling in healthy cells or a liability during trauma. Recombinant N-type channels expressed in HEK cells revealed a spectrum of mechano-responses. When hydrostatic pressure inflated cells under whole-cell clamp, capacitance was unchanged, but peak current reversibly increased ~1.5-fold, correlating with inflation, not applied pressure. Additionally, stretch transiently increased the open-state inactivation rate, irreversibly increased the closed-state inactivation rate, and left-shifted inactivation without affecting the activation curve or rate. Irreversible mechano-responses proved to be mechanically accelerated components of run-down; they were not evident in cell-attached recordings where, however, reversible stretch-induced increases in peak current persisted. T-type channels (alpha(1I) subunit only) were mechano-insensitive when expressed alone or when coexpressed with N-type channels (alpha(1B) and two auxiliary subunits) and costimulated with stretch that augmented N-type current. Along with the cell-attached results, this differential effect indicates that N-type mechanosensitivity did not depend on the recording situation. The insensitivity of T-type currents to stretch suggested that N-type mechano-responses might arise from primary/auxiliary subunit interactions. However, in single-channel recordings, N-type currents exhibited reversible stretch-induced increases in NP(o) whether the alpha(1B) subunit was expressed alone or with auxiliary subunits. These findings set the stage for the molecular dissection of calcium current mechanosensitivity.
Calabrese
Barbara
B
Department of Neurosciences, Ottawa Health Research Institute, Ottawa, Ontario K1Y 4E9, Canada.
Tabarean
Iustin V
IV
Juranka
Peter
P
Morris
Catherine E
CE
D001464:Barium / Q000737:chemistry; D001921:Brain / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000737:chemistry* / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004594:Electrophysiology; D006801:Humans; D007700:Kinetics; D018715:Microscopy, Video; D009474:Neurons / Q000378:metabolism; D016011:Normal Distribution; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors
D020864:Calcium Channels, N-Type; D018076:DNA, Complementary; D011994:Recombinant Proteins; D001464:Barium