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Structural features determining differential receptor regulation of neuronal Ca channels.

ABSTRACT: Dihydropyridine-insensitive Ca channels are subject to direct receptor G-protein-mediated inhibition to differing extents. alpha1B channels are much more strongly modulated than alpha1E channels. To understand the structural basis for this difference, we have constructed and expressed various alpha1B and alpha1E chimeric Ca channels and examined their regulation by kappa-opioid receptors. Replacement of the first membrane-spanning domain of alpha1E with the corresponding region of alpha1B resulted in a chimeric Ca channel that was modulated by kappa-opioid receptors to a significantly greater extent than alpha1E. Transfer of the N terminus and I/II loop from alpha1B in addition to domain I resulted in a chimeric channel that was modulated to the same extent as alpha1B. Other regions of the molecule do not appear to contribute significantly to the degree of inhibition obtained, although the C terminus may contribute to facilitation.

SUBMITTER: Simen AA

PROVIDER: S-EPMC6793165 | biostudies-literature | 1998 May

REPOSITORIES: biostudies-literature

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Structural features determining differential receptor regulation of neuronal Ca channels.

Simen A A AA Miller R J RJ

The Journal of neuroscience : the official journal of the Society for Neuroscience 19980501 10

Dihydropyridine-insensitive Ca channels are subject to direct receptor G-protein-mediated inhibition to differing extents. alpha1B channels are much more strongly modulated than alpha1E channels. To understand the structural basis for this difference, we have constructed and expressed various alpha1B and alpha1E chimeric Ca channels and examined their regulation by kappa-opioid receptors. Replacement of the first membrane-spanning domain of alpha1E with the corresponding region of alpha1B result ...[more]

PMID: 9570799

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Project description:Stac protein (named for its SH3- and cysteine-rich domains) was first identified in brain 20 years ago and is currently known to have three isoforms. Stac2, Stac1, and Stac3 transcripts are found at high, modest, and very low levels, respectively, in the cerebellum and forebrain, but their neuronal functions have been little investigated. Here, we tested the effects of Stac proteins on neuronal, high-voltage-activated Ca2+ channels. Overexpression of the three Stac isoforms eliminated Ca2+-dependent inactivation (CDI) of l-type current in rat neonatal hippocampal neurons (sex unknown), but not CDI of non-l-type current. Using heterologous expression in tsA201 cells (together with β and α2-δ1 auxiliary subunits), we found that CDI for CaV1.2 and CaV1.3 (the predominant, neuronal l-type Ca2+ channels) was suppressed by all three Stac isoforms, whereas CDI for the P/Q channel, CaV2.1, was not. For CaV1.2, the inhibition of CDI by the Stac proteins appeared to involve their direct interaction with the channel's C terminus. Within the Stac proteins, a weakly conserved segment containing ∼100 residues and linking the structurally conserved PKC C1 and SH3_1 domains was sufficient to fully suppress CDI. The presence of CDI for l-type current in control neonatal neurons raised the possibility that endogenous Stac levels are low in these neurons and Western blotting indicated that the expression of Stac2 was substantially increased in adult forebrain and cerebellum compared with neonate. Together, our results indicate that one likely function of neuronal Stac proteins is to tune Ca2+ entry via neuronal l-type channels.SIGNIFICANCE STATEMENT Stac protein, first identified 20 years ago in brain, has recently been found to be essential for proper trafficking and function of the skeletal muscle l-type Ca2+ channel and is the site of mutations causing a severe, inherited human myopathy. In neurons, however, functions for Stac protein have remained unexplored. Here, we report that one likely function of neuronal Stac proteins is tuning Ca2+ entry via l-type, but not that via non-l-type, Ca2+ channels. Moreover, there is a large postnatal increase in protein levels of the major neuronal isoform (Stac2) in forebrain and cerebellum, which could provide developmental regulation of l-type channel Ca2+ signaling in these brain regions.

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Structural features determining differential receptor regulation of neuronal Ca channels.

Publications

Structural features determining differential receptor regulation of neuronal Ca channels.

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