Dataset Information

The beta subunit of voltage-gated Ca2+ channels interacts with and regulates the activity of a novel isoform of Pax6.

ABSTRACT: Ca(2+) channel beta subunits (Ca(v)betas) are essential for regulating the surface expression and gating of high voltage-activated Ca(2+) channels through their interaction with Ca(2+) channel alpha(1) subunits. In efforts to uncover new interacting partners and new functions for Ca(v)beta, we identified a new splicing isoform of Pax6, a transcription factor crucial for the development of the eye, nose, brain, and pancreas. Pax6 contains two DNA binding domains (paired domain and homeodomain), a glycine-rich linker connecting these two domains and a C-terminal proline-, serine-, and threonine-rich transactivation domain. The protein sequence and function of Pax6 are highly conserved from invertebrate to human. The newly isolated isoform, named Pax6(S), retains the paired domain, linker, and homeodomain of Pax6, but its C terminus is composed of a truncated classic proline, serine, and threonine domain and a unique S tail. Pax6(S) shows a similar level of transcriptional activity in vitro as does Pax6, but only in primates is the protein sequence highly conserved. Its spatial-temporal expression profiles are also different from those of Pax6. These divergences suggest a noncanonical role of Pax6(S) during development. The interaction between Pax6(S) and Ca(v)beta is mainly endowed by the S tail. Co-expression of Pax6(S) with a Ca(2+) channel complex containing the beta(3) subunit in Xenopus oocytes does not affect channel properties. Conversely, however, beta(3) is able to suppress the transcriptional activity of Pax6(S). Furthermore, in the presence of Pax6(S), beta(3) is translocated from the cytoplasm to the nucleus. These results suggest that full-length Ca(v)beta may act directly as a transcription regulator independent of its role in regulating Ca(2+) channel activity.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC2807309 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The beta subunit of voltage-gated Ca2+ channels interacts with and regulates the activity of a novel isoform of Pax6.

Zhang Yun Y Yamada Yoichi Y Fan Mingming M Bangaru Saroja D SD Lin Bochao B Yang Jian J

The Journal of biological chemistry 20091116 4

Ca(2+) channel beta subunits (Ca(v)betas) are essential for regulating the surface expression and gating of high voltage-activated Ca(2+) channels through their interaction with Ca(2+) channel alpha(1) subunits. In efforts to uncover new interacting partners and new functions for Ca(v)beta, we identified a new splicing isoform of Pax6, a transcription factor crucial for the development of the eye, nose, brain, and pancreas. Pax6 contains two DNA binding domains (paired domain and homeodomain), a ...[more]

PMID: 19917615

Similar Datasets

Project description:High voltage-activated Ca2+ (Ca(V)) channels are protein complexes containing pore-forming α1 and auxiliary β and α2δ subunits. The subcellular localization and membrane interactions of the β subunits play a crucial role in regulating Ca(V) channel inactivation and its lipid sensitivity. Here, we investigated the effects of membrane phosphoinositide (PI) turnover on Ca(V)2.2 channel function. The β2 isoform β2e associates with the membrane through electrostatic and hydrophobic interactions. Using chimeric β subunits and liposome-binding assays, we determined that interaction between the N-terminal 23 amino acids of β2e and anionic phospholipids was sufficient for β2e membrane targeting. Binding of the β2e subunit N terminus to liposomes was significantly increased by inclusion of 1% phosphatidylinositol 4,5-bisphosphate (PIP2) in the liposomes, suggesting that, in addition to phosphatidylserine, PIs are responsible for β2e targeting to the plasma membrane. Membrane binding of the β2e subunit slowed Ca(V)2.2 current inactivation. When membrane phosphatidylinositol 4-phosphate and PIP2 were depleted by rapamycin-induced translocation of pseudojanin to the membrane, however, channel opening was decreased and fast inactivation of Ca(V)2.2(β2e) currents was enhanced. Activation of the M1 muscarinic receptor elicited transient and reversible translocation of β2e subunits from membrane to cytosol, but not that of β2a or β3, resulting in fast inactivation of Ca(V)2.2 channels with β2e. These results suggest that membrane targeting of the β2e subunit, which is mediated by nonspecific electrostatic insertion, is dynamically regulated by receptor stimulation, and that the reversible association of β2e with membrane PIs results in functional changes in Ca(V) channel gating. The phospholipid-protein interaction observed here provides structural insight into mechanisms of membrane-protein association and the role of phospholipids in ion channel regulation.

Project description:Voltage-dependent Na+ channel activation underlies action potential generation fundamental to cellular excitability. In skeletal and cardiac muscle this triggers contraction via ryanodine-receptor (RyR)-mediated sarcoplasmic reticular (SR) Ca2+ release. We here review potential feedback actions of intracellular [Ca2+] ([Ca2+]i) on Na+ channel activity, surveying their structural, genetic and cellular and functional implications, translating these to their possible clinical importance. In addition to phosphorylation sites, both Nav1.4 and Nav1.5 possess potentially regulatory binding sites for Ca2+ and/or the Ca2+-sensor calmodulin in their inactivating III-IV linker and C-terminal domains (CTD), where mutations are associated with a range of skeletal and cardiac muscle diseases. We summarize in vitro cell-attached patch clamp studies reporting correspondingly diverse, direct and indirect, Ca2+ effects upon maximal Nav1.4 and Nav1.5 currents (Imax) and their half-maximal voltages (V1/2) characterizing channel gating, in cellular expression systems and isolated myocytes. Interventions increasing cytoplasmic [Ca2+]i down-regulated Imax leaving V1/2 constant in native loose patch clamped, wild-type murine skeletal and cardiac myocytes. They correspondingly reduced action potential upstroke rates and conduction velocities, causing pro-arrhythmic effects in intact perfused hearts. Genetically modified murine RyR2-P2328S hearts modelling catecholaminergic polymorphic ventricular tachycardia (CPVT), recapitulated clinical ventricular and atrial pro-arrhythmic phenotypes following catecholaminergic challenge. These accompanied reductions in action potential conduction velocities. The latter were reversed by flecainide at RyR-blocking concentrations specifically in RyR2-P2328S as opposed to wild-type hearts, suggesting a basis for its recent therapeutic application in CPVT. We finally explore the relevance of these mechanisms in further genetic paradigms for commoner metabolic and structural cardiac disease.

Dataset Information

The beta subunit of voltage-gated Ca2+ channels interacts with and regulates the activity of a novel isoform of Pax6.

Publications

The beta subunit of voltage-gated Ca2+ channels interacts with and regulates the activity of a novel isoform of Pax6.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets