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Quality control at the cell surface prevents accumulation of damaged L-type CaV1.2 calcium channels

ABSTRACT: Defective ion channel turnover and clearance of damaged proteins are associated with aging and neurodegeneration. The L-type CaV1.2 voltage-gated calcium channel mediate depolarization-induced calcium signals in heart and brain. Here, we determined the interaction surface between the L-type calcium channel CaVβ subunit and actin using cross-linking mass spectrometry and protein-protein docking, and uncovered a role in replenishing damaged CaV1.2 channels. Computational and in vitro mutagenesis identified hotspots in CaVβ that decrease its affinity for actin but not for CaV1.2. Coexpression of an actin-association-deficient CaVβ mutant with the CaV1.2 channel downregulated current amplitudes with a concomitant reduction in the number of functionally available channels. Neither alterations in the single-channel properties nor changes in the total number of channels at the cell surface were found, indicating that current inhibition resulted from a build-up of conduction-defective channels. Our findings established CaVβ–actin interaction as a key player for selective monitoring and clearing corrupted CaV proteins to ensure the maintenance of a functional pool of channels and proper calcium signal transduction. The CaVβ–actin molecular model introduces a potentially druggable protein-protein interface to intervene CaV-mediated signaling processes.

INSTRUMENT(S): Orbitrap Eclipse, Q Exactive

ORGANISM(S): Escherichia Coli Oryctolagus Cuniculus (rabbit)

SUBMITTER: Beatrix Santiago-Schuebel

LAB HEAD: Beatrix Santiago

PROVIDER: PXD044723 | Pride | 2024-02-16

REPOSITORIES: Pride

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Project description:Voltage gated calcium channels play a central role in regulating the electrical and biochemical properties of neurons and muscle cells. Cells coordinate the expression of voltage gated calcium channels with the expression of other proteins that regulate membrane potential and calcium homeostasis. We report that the C-terminus of CaV 1.2, an L-type calcium channel (LTC) contains a C-terminal fragment that translocates to the nucleus and regulates transcription. This calcium channel associated transcription factor (CCAT) associates with transcriptional co-regulators such as p54nrb/NonO and binds to endogenous promoters. CCAT regulates the expression of gap junctions, sodium calcium exchangers, NMDA receptors, potassium channels and other proteins that regulate neuronal signaling. Electrical activity and developmental processes regulate the nuclear localization of CCAT, suggesting that the CCAT integrates information about the number of LTCs with information about the developmental history and electrical activity of a cell. These findings provide the first evidence that voltage gated calcium channels can directly activate transcription and suggest a novel mechanism linking voltage gated channels to the function and differentiation of excitable cells. Experiment Overall Design: The goal of these experiments was to identify the genes that are regulated by CCAT, a novel transcription factor derived from the C-terminus of CaV1.2. Neuro2A neuroblastoma cells were transfected with the last 503 AA of CaV1.2 which is full length CCAT (CCAT FL) or with the last 280 AA of CaV1.2, a form of CCAT that lacks the transcriptional activation domain (CCAT DTA). The mRNA from either CCAT FL or CCAT DTA expressing cells was hybridized to Agilent mouse genome microarrays along with mRNA from untransfected neuro2A cells (CCAT FL or DTA A series). Subsequent investigation revealed that transfection with the PA1 plasmid by itself increases the expression of some genes. To control for this effect we compared Neuro2A cells transfected with full length CCAT (in PA1) with Neuro2A cells transfectected with PA1 alone (CCAT FL B series). The microarray data was analyzed with the Rossetta Luminator gene expression data analysis system.

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Quality control at the cell surface prevents accumulation of damaged L-type CaV1.2 calcium channels

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