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Interaction between G proteins and accessory subunits in the regulation of 1B calcium channels in Xenopus oocytes

Interaction between G proteins and accessory subunits in the regulation of 1B calcium channels in Xenopus oocytes
Interaction between G proteins and accessory subunits in the regulation of 1B calcium channels in Xenopus oocytes
1
The accessory β subunits of voltage-dependent Ca2+ channels (VDCCs) have been shown to regulate their biophysical properties and have also been suggested to antagonise the G protein inhibition of N-type (α1B), P/Q-type (α1A) and α1E channels. Here we have examined the voltage-dependent involvement of the four neuronal isoforms (β1b, β2a, β3 and β4) in the process of G protein modulation of α1B Ca2+ channels.

2
All β subunits hyperpolarised α1B current activation, and all antagonised the G protein-mediated depolarisation of current activation. However, except in the case of β2a, there was no generalised reduction by β subunits in the maximal extent of receptor-mediated inhibition of α1B current.

3
In addition, all VDCC β subunits enhanced the rate of current facilitation at +100 mV, for both receptor-mediated and tonic modulation. The rank order for enhancement of facilitation rate was β3 > β4 > β1b > β2a. In contrast, the amount of voltage-dependent facilitation during tonic modulation was reduced by β subunit co-expression, despite the fact that the apparent Gβγ dissociation rate at +100 mV was enhanced by β subunits to a similar level as for agonist-induced modulation.

4
Our data provide evidence that G protein activation antagonises Ca2+-channel β subunit-induced hyperpolarisation of current activation. Conversely, co-expression of all β subunits increases the apparent Gβγ dimer dissociation rate during a depolarising prepulse. This latter feature suggests the co-existence of bound Ca2+-channel β subunits and Gβγ dimers on the α1B subunits. Future work will determine how the interaction between Gβγ dimers and Ca2+-channel β subunits with α1B results in a functional antagonism at the molecular level.
0022-3751
419-432
Cantí, C
83f0634d-9693-46a7-bfbf-63d6f684a1bd
Bogdanov, Y
0c970999-e191-4f1b-90d9-7bf25a5d5b4b
Dolphin, AC
43d0cb0b-f17c-4ca2-b099-894f11b51d6e
Cantí, C
83f0634d-9693-46a7-bfbf-63d6f684a1bd
Bogdanov, Y
0c970999-e191-4f1b-90d9-7bf25a5d5b4b
Dolphin, AC
43d0cb0b-f17c-4ca2-b099-894f11b51d6e

Cantí, C, Bogdanov, Y and Dolphin, AC (2000) Interaction between G proteins and accessory subunits in the regulation of 1B calcium channels in Xenopus oocytes. The Journal of Physiology, 527 (3), 419-432. (doi:10.1111/j.1469-7793.2000.t01-1-00419.x).

Record type: Article

Abstract

1
The accessory β subunits of voltage-dependent Ca2+ channels (VDCCs) have been shown to regulate their biophysical properties and have also been suggested to antagonise the G protein inhibition of N-type (α1B), P/Q-type (α1A) and α1E channels. Here we have examined the voltage-dependent involvement of the four neuronal isoforms (β1b, β2a, β3 and β4) in the process of G protein modulation of α1B Ca2+ channels.

2
All β subunits hyperpolarised α1B current activation, and all antagonised the G protein-mediated depolarisation of current activation. However, except in the case of β2a, there was no generalised reduction by β subunits in the maximal extent of receptor-mediated inhibition of α1B current.

3
In addition, all VDCC β subunits enhanced the rate of current facilitation at +100 mV, for both receptor-mediated and tonic modulation. The rank order for enhancement of facilitation rate was β3 > β4 > β1b > β2a. In contrast, the amount of voltage-dependent facilitation during tonic modulation was reduced by β subunit co-expression, despite the fact that the apparent Gβγ dissociation rate at +100 mV was enhanced by β subunits to a similar level as for agonist-induced modulation.

4
Our data provide evidence that G protein activation antagonises Ca2+-channel β subunit-induced hyperpolarisation of current activation. Conversely, co-expression of all β subunits increases the apparent Gβγ dimer dissociation rate during a depolarising prepulse. This latter feature suggests the co-existence of bound Ca2+-channel β subunits and Gβγ dimers on the α1B subunits. Future work will determine how the interaction between Gβγ dimers and Ca2+-channel β subunits with α1B results in a functional antagonism at the molecular level.

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Published date: 1 September 2000

Identifiers

Local EPrints ID: 469804
URI: http://eprints.soton.ac.uk/id/eprint/469804
ISSN: 0022-3751
PURE UUID: 5e14e7c5-466d-4e69-bbae-3ca3ead87f36
ORCID for Y Bogdanov: ORCID iD orcid.org/0000-0003-4667-5890

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Date deposited: 26 Sep 2022 16:40
Last modified: 17 Mar 2024 03:37

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Contributors

Author: C Cantí
Author: Y Bogdanov ORCID iD
Author: AC Dolphin

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