Loss of the Auxiliary α 2δ1 Voltage-Sensitive Calcium Channel Subunit Impairs Bone Formation and Anabolic Responses to Mechanical Loading

Authors

Madison M Kelly
Karan Sharma
Christian S Wright
Xin Yi
Perla C Reyes Fernandez
Aaron T Gegg
Taylor A Gorrell
Megan L Noonan
Ahmed Baghdady
Jacob A Sieger
Annette C Dolphin
Stuart J Warden
Padmini Deosthale
Lilian I Plotkin
Uma Sankar
Julia M Hum
Alexander G Robling
Mary C Farach-Carson
William R Thompson

Publication Date

1-1-2024

Journal

JBMR Plus

Abstract

Voltage-sensitive calcium channels (VSCCs) influence bone structure and function, including anabolic responses to mechanical loading. While the pore-forming (α1) subunit of VSCCs allows Ca2+ influx, auxiliary subunits regulate the biophysical properties of the pore. The α2δ1 subunit influences gating kinetics of the α1 pore and enables mechanically induced signaling in osteocytes; however, the skeletal function of α2δ1 in vivo remains unknown. In this work, we examined the skeletal consequences of deleting Cacna2d1, the gene encoding α2δ1. Dual-energy X-ray absorptiometry and microcomputed tomography imaging demonstrated that deletion of α2δ1 diminished bone mineral content and density in both male and female C57BL/6 mice. Structural differences manifested in both trabecular and cortical bone for males, while the absence of α2δ1 affected only cortical bone in female mice. Deletion of α2δ1 impaired skeletal mechanical properties in both sexes, as measured by three-point bending to failure. While no changes in osteoblast number or activity were found for either sex, male mice displayed a significant increase in osteoclast number, accompanied by increased eroded bone surface and upregulation of genes that regulate osteoclast differentiation. Deletion of α2δ1 also rendered the skeleton insensitive to exogenous mechanical loading in males. While previous work demonstrates that VSCCs are essential for anabolic responses to mechanical loading, the mechanism by which these channels sense and respond to force remained unclear. Our data demonstrate that the α2δ1 auxiliary VSCC subunit functions to maintain baseline bone mass and strength through regulation of osteoclast activity and also provides skeletal mechanotransduction in male mice. These data reveal a molecular player in our understanding of the mechanisms by which VSCCs influence skeletal adaptation.

Keywords

α2δ1 subunit, mechanotransduction, voltage-sensitive calcium channel, bone formation, loading

Comments

Supplementary Materials

PMID: 38505532