S100A1 modulates skeletal muscle contraction by desensitizing calcium activation of isometric tension, stiffness and ATPase

摘要

>S100, a subfamily of the EF-hand type calcium sensing proteins, is implicated in many cellular functions including muscle contractility. Two isoforms, S100A1 and S100B, at 2–10 μM significantly inhibit active tension, stiffness and ATPase of skinned single rabbit psoas muscle fibers at sub-maximal (pCa ∼6.1-5.6), but not at maximal levels of activation (pCa 4.0). S100A1 is a more potent inhibitor than S100B. Hill analysis of the ATPase–pCa and tension–pCa curves indicates that these proteins reduce calcium sensitivity and enhance the cooperativity toward calcium. We propose S100A1, and perhaps S100B, are viable candidates as physiological modulators of muscle contraction.