Phospholipase C-dependent Ca2+-sensing pathways leading to endocytosis and inhibition of the plasma membrane vacuolar H+-ATPase in osteoclasts

作者：Sakai Hiromu; Moriura Yoshie; Notomi Takuya; Kawawaki Junko; Ohnishi Keiko; Kuno Miyuki^*

来源：American Journal of Physiology - Cell Physiology, 2010, 299(3): C570-C578.

DOI：10.1152/ajpcell.00486.2009

• proton current
• cell capacitance
• dynamin
• cytosolic ca(2+), calmodulin

Sakai H, Moriura Y, Notomi T, Kawawaki J, Ohnishi K, Kuno M. Phospholipase C-dependent Ca2+-sensing pathways leading to endocytosis and inhibition of the plasma membrane vacuolar H+-ATPase in osteoclasts. Am J Physiol Cell Physiol 299: C570-C578, 2010. First published June 30, 2010; doi: 10.1152/ajpcell.00486.2009.-In osteoclasts, elevation of extracellular Ca2+ is an endogenous signal that inhibits bone resorption. We recently found that an elevation of extracellular Ca2+ decreased proton extrusion through the plasma membrane vacuolar H+-ATPase (V-ATPase) rapidly. In this study we investigated mechanisms underlying this early Ca2+-sensing response, particularly in reference to the activity of the plasma membrane V-ATPase and to membrane retrieval. Whole cell clamp recordings allowed us to measure the V-ATPase currents and the cell capacitance (Cm) simultaneously. Cm is a measure of cell surface. Extracellular Ca2+ (2.5-40 mM) decreased Cm and the V-ATPase current simultaneously. The decreased Cm, together with the enhanced uptake of a lipophilic dye (FM1-43), indicated that Ca2+ facilitated endocytosis. The endocytosis was blocked by dynamin inhibitors (dynasore and dynamin-inhibitory peptide), by small interfering RNA (siRNA) targeting for dynanmin-2 and also by bafilomycin A(1), a blocker of V-ATPases. The extracellular Ca2+-induced endocytosis and inhibition of the V-ATPase current were diminished by a phospholipase C inhibitor (U73122) and siRNA targeting for phospholipase C gamma 2 subunit. Holding the cytosolic Ca2+ at either high (0.5-5 mu M) or low levels or inhibiting calmodulin by an inhibitor (W7) or an antibody (anti-CaM) decreased the stimulated endocytosis and the inhibition of the V-ATPase current. These data suggest that extracellular Ca2+ facilitated dynamin-and V-ATPase-dependent endocytosis in association with an inhibition of the plasma membrane V-ATPase. Phospholipase C, cytosolic Ca2+, and calmodulin were involved in the signaling pathways. Membrane retrieval and the plasma membrane V-ATPase activity may cooperate during the early phase of Ca2+-sensing response in osteoclasts.

• 出版日期2010-9