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Biophys J, November 2002, p. 2560-2574, Vol. 83, No. 5

Mechanosensitivity of N-Type Calcium Channel Currents

Barbara Calabrese,* Iustin V. Tabarean,* Peter Juranka,* and Catherine E. Morris*dagger

 *Department of Neurosciences, Ottawa Health Research Institute, and  dagger Department of Medicine, University of Ottawa, Ottawa, Ontario K1Y 4E9, Canada

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 NPo 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.

Biophys J, November 2002, p. 2560-2574, Vol. 83, No. 5
© 2002 by the Biophysical Society   0006-3495/02/11/2560/15  $2.00


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