Dataset Information

Competition between ?-actinin and Ca²?-calmodulin controls surface retention of the L-type Ca²? channel Ca(V)1.2.

ABSTRACT: Regulation of neuronal excitability and cardiac excitation-contraction coupling requires the proper localization of L-type Ca²? channels. We show that the actin-binding protein ?-actinin binds to the C-terminal surface targeting motif of ?11.2, the central pore-forming Ca(V)1.2 subunit, in order to foster its surface expression. Disruption of ?-actinin function by dominant-negative or small hairpin RNA constructs reduces Ca(V)1.2 surface localization in human embryonic kidney 293 and neuronal cultures and dendritic spine localization in neurons. We demonstrate that calmodulin displaces ?-actinin from their shared binding site on ?11.2 upon Ca²? influx through L-type channels, but not through NMDAR, thereby triggering loss of Ca(V)1.2 from spines. Coexpression of a Ca²?-binding-deficient calmodulin mutant does not affect basal Ca(V)1.2 surface expression but inhibits its internalization upon Ca²? influx. We conclude that ?-actinin stabilizes Ca(V)1.2 at the plasma membrane and that its displacement by Ca²?-calmodulin triggers Ca²?-induced endocytosis of Ca(V)1.2, thus providing an important negative feedback mechanism for Ca²? influx.

SUBMITTER: Hall DD

PROVIDER: S-EPMC4570828 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature

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Competition between α-actinin and Ca²⁺-calmodulin controls surface retention of the L-type Ca²⁺ channel Ca(V)1.2.

Hall Duane D DD Dai Shuiping S Tseng Pang-Yen PY Malik Zulfiqar Z Nguyen Minh M Matt Lucas L Schnizler Katrin K Shephard Andrew A Mohapatra Durga P DP Tsuruta Fuminori F Dolmetsch Ricardo E RE Christel Carl J CJ Lee Amy A Burette Alain A Weinberg Richard J RJ Hell Johannes W JW

Neuron 20130501 3

Regulation of neuronal excitability and cardiac excitation-contraction coupling requires the proper localization of L-type Ca²⁺ channels. We show that the actin-binding protein α-actinin binds to the C-terminal surface targeting motif of α11.2, the central pore-forming Ca(V)1.2 subunit, in order to foster its surface expression. Disruption of α-actinin function by dominant-negative or small hairpin RNA constructs reduces Ca(V)1.2 surface localization in human embryonic kidney 293 and neuronal cu ...[more]

PMID: 23664615

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Project description:Bone remodeling of the auditory ossicles and the otic capsule is highly restricted and tightly controlled by the osteoprotegerin (OPG)/receptor activator of nuclear factor kappa-Β ligand (RANKL)/receptor activator of nuclear factor kappa-Β (RANK) system. In these bony structures, a pathological decrease in OPG expression stimulates osteoclast differentiation and excessive resorption followed by accrual of sclerotic bone, ultimately resulting in the development of otosclerosis, a leading cause of deafness in adults. Understanding the signaling pathways involved in maintaining OPG expression in the ear would shed light on the pathophysiology of otosclerosis and other ear bone-related diseases. We and others previously demonstrated that Ca2+ signaling through the L-type CaV1.2 Ca2+ channel positively regulates OPG expression and secretion in long bone osteoblasts and their precursor cells in vitro and in vivo. Whether CaV1.2 regulates OPG expression in ear bones has not been investigated. We drove expression of a gain-of-function CaV1.2 mutant channel (CaV1.2TS) using Col2a1-Cre, which we found to target osteochondral/osteoblast progenitors in the auditory ossicles and the otic capsule. Col2a1-Cre;CaV1.2TS mice displayed osteopetrosis of these bones shown by μCT 3D reconstruction, histological analysis, and lack of bone sculpting, findings similar to phenotypes seen in mice with an osteoclast defect. Consistent with those observations, we found that Col2a1-Cre;CaV1.2TS mutant mice showed reduced osteoclasts in the otic capsule, upregulated mRNA expression of Opg and Opg/Rankl ratio, and increased mRNA expression of osteoblast differentiation marker genes in the otic capsule, suggesting both an anti-catabolic and anabolic effect of CaV1.2TS mutant channel contributed to the observed morphological changes of the ear bones. Further, we found that Col2a1-Cre;CaV1.2TS mice experienced hearing loss and displayed defects of body balance in behavior tests, confirming that the CaV1.2-dependent Ca2+ influx affects bone structure in the ear and consequent hearing and vestibular functions. Together, these data support our hypothesis that Ca2+ influx through CaV1.2TS promotes OPG expression from osteoblasts, thereby affecting bone modeling/remodeling in the auditory ossicles and the otic capsule. These data provide insight into potential pathological mechanisms underlying perturbed OPG expression and otosclerosis.

Dataset Information

Competition between ?-actinin and Ca²?-calmodulin controls surface retention of the L-type Ca²? channel Ca(V)1.2.

Publications

Competition between α-actinin and Ca²⁺-calmodulin controls surface retention of the L-type Ca²⁺ channel Ca(V)1.2.

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