Abstract
Voltage-gated Ca(2+) channels play a key role in initiating muscle excitation-contraction coupling, neurotransmitter release, gene expression, and hormone secretion. The association of CaV1.2 with a supramolecular complex impacts trafficking, localization, turnover, and, most importantly, multifaceted regulation of its function in the heart. Several studies hint at an important role for the C terminus of the α1C subunit as a hub for multidimensional regulation of CaV1.2 channel trafficking and function. Recent studies have demonstrated an important role for the four-residue PDZ binding motif at the C terminus of α1C in interacting with scaffold proteins containing PDZ domains, in the subcellular localization of CaV1.2 in neurons, and in the efficient signaling to cAMP-response element-binding protein in neurons. However, the role of the α1C PDZ ligand domain in the heart is not known. To determine whether the α1C PDZ motif is critical for CaV1.2 trafficking and function in cardiomyocytes, we generated transgenic mice with inducible expression of an N-terminal FLAG epitope-tagged dihydropyridine-resistant α1C with the PDZ motif deleted (ΔPDZ). These mice were crossed with α-myosin heavy chain reverse transcriptional transactivator transgenic mice, and the double-transgenic mice were fed doxycycline. The ΔPDZ channels expressed, trafficked to the membrane, and supported robust excitation-contraction coupling in the presence of nisoldipine, a dihydropyridine Ca(2+) channel blocker, providing functional evidence that they appropriately target to dyads. The ΔPDZ Ca(2+) channels were appropriately regulated by isoproterenol and forskolin. These data indicate that the α1C PDZ motif is not required for surface trafficking, localization to the dyad, or adrenergic stimulation of CaV1.2 in adult cardiomyocytes.
Highlights
The mechanisms responsible for CaV1.2 regulation by the ␣1C C terminus are unknown
Generation of Inducible, Cardiac-specific ⌬PDZ a1C Transgenic Mice—A class I PDZ domain-binding motif VSXL is present in the cardiac/neuronal ␣1C subunit, conforming to the consensus sequence X[T/S]XCOOH, where X is any residue and is a hydrophobe [34]
The PDZ domain-binding motif is conserved across many species, including human, rabbit, rodents, and zebrafish and in the Caenorhabditis elegans L-type Ca2ϩ channel subunit [23] (Fig. 1)
Summary
The mechanisms responsible for CaV1.2 regulation by the ␣1C C terminus are unknown. Results: Trafficking, basal function, and adrenergic modulation of CaV1.2 were not altered in cardiomyocytes of transgenic mice expressing PDZ-deleted ␣1C. ␣ 1904 1C that did make it to the surface in knockin mouse neonatal cardiomyocytes was insensitive to -adrenergic modulation, suggesting a role of the distal C terminus of ␣1C in mediating sympathetic nervous system activation of the Ca2ϩ channel in the heart [17, 18]. These studies identify an important role for the distal C terminus of ␣1C in regulating CaV1.2 trafficking and function in the heart, but the precise mechanisms and determinants underlying its role are unknown. ␣1C C terminus, the role of many of these putative interaction sites in modulating CaV1.2 trafficking and function have not yet been tested in cardiomyocytes (12–14, 19 –21)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
