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Association of the ?(2)?(1) subunit with Ca(v)3.2 enhances membrane expression and regulates mechanically induced ATP release in MLO-Y4 osteocytes.

ABSTRACT: Voltage-sensitive calcium channels (VSCCs) mediate signaling events in bone cells in response to mechanical loading. Osteoblasts predominantly express L-type VSCCs composed of the ?(1) pore-forming subunit and several auxiliary subunits. Osteocytes, in contrast, express T-type VSCCs and a relatively small amount of L-type ?(1) subunits. Auxiliary VSCC subunits have several functions, including modulating gating kinetics, trafficking of the channel, and phosphorylation events. The influence of the ?(2)? auxiliary subunit on T-type VSCCs and the physiologic consequences of that association are incompletely understood and have yet to be investigated in bone. In this study we postulated that the auxiliary ?(2) ? subunit of the VSCC complex modulates mechanically regulated ATP release in osteocytes via its association with the T-type Ca(v) 3.2 (?(1H) ) subunit. We demonstrated by reverse-transcriptase polymerase chain reaction, Western blotting, and immunostaining that MLO-Y4 osteocyte-like cells express the T-type Ca(v)3.2(?(1H)) subunit more abundantly than the L-type Ca(v)1.2 (?(1C)) subunit. We also demonstrated that the ?(2) ?(1) subunit, previously described as an L-type auxiliary subunit, complexes with the T-type Ca(v)3.2 (?(1H)) subunit in MLO-Y4?cells. Interestingly, siRNA-mediated knockdown of ?(2) ?(1) completely abrogated ATP release in response to membrane stretch in MLO-Y4?cells. Additionally, knockdown of the ?(2)?(1) subunit resulted in reduced ERK1/2 activation. Together these data demonstrate a functional VSCC complex. Immunocytochemistry following ?(2)?(1) knockdown showed decreased membrane localization of Ca(v) 3.2 (?(1H)) at the plasma membrane, suggesting that the diminished ATP release and ERK1/2 activation in response to membrane stretch resulted from a lack of Ca(v) 3.2 (?(1H)) at the cell membrane.

SUBMITTER: Thompson WR

PROVIDER: S-EPMC4478606 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Association of the α(2)δ(1) subunit with Ca(v)3.2 enhances membrane expression and regulates mechanically induced ATP release in MLO-Y4 osteocytes.

Thompson William R WR Majid Amber S AS Czymmek Kirk J KJ Ruff Albert L AL García Jesús J Duncan Randall L RL Farach-Carson Mary C MC

Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research 20110901 9

Voltage-sensitive calcium channels (VSCCs) mediate signaling events in bone cells in response to mechanical loading. Osteoblasts predominantly express L-type VSCCs composed of the α(1) pore-forming subunit and several auxiliary subunits. Osteocytes, in contrast, express T-type VSCCs and a relatively small amount of L-type α(1) subunits. Auxiliary VSCC subunits have several functions, including modulating gating kinetics, trafficking of the channel, and phosphorylation events. The influence of th ...[more]

PMID: 21638318

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Dataset Information

Association of the ?(2)?(1) subunit with Ca(v)3.2 enhances membrane expression and regulates mechanically induced ATP release in MLO-Y4 osteocytes.

Publications

Association of the α(2)δ(1) subunit with Ca(v)3.2 enhances membrane expression and regulates mechanically induced ATP release in MLO-Y4 osteocytes.

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