Why the study?
Do cardiac alpha(1) subunits exhibit voltage-dependent facilitation independently of the beta subunit?
Do cardiac alpha(1) subunits exhibit voltage-dependent facilitation independently of the beta subunit?
Cardiac alpha(1) subunits exhibit voltage-dependent facilitation due to their intrinsic structure, independent of accessory beta subunits or other regulatory proteins.
Answers are grounded in this paper and cite their sources.
Does not inform clinical Ca channel targeting; leaves open alpha1-intrinsic facilitation in native myocytes.
Strong depolarization pulses facilitate L-type Ca(2+) channels in various cell types including cardiac myocytes. The mechanisms underlying prepulse facilitation are controversial with respect to the requirements for channel subunits, cAMP-dependent protein kinase, and additional anchor proteins. The properties of voltage-dependent facilitation of the L-type Ca(2+) channel was studied in recombinant cardiac alpha(1) subunits with or without cardiac beta subunit, expressed in Chinese hamster fibroblast cells. The magnitude of voltage-dependent I(Ba) facilitation in the alpha(1) subunit channel is dependent on the duration of the prepulse as well as on the interval duration between prepulse and test pulse. The characteristics of this facilitation were not affected by coexpression of the beta subunit. These results indicate that cardiac alpha(1) subunits exhibit voltage-dependent facilitation because of their own intrinsic structure, independent of any other accessory subunit or additional regulatory proteins, and that cardiac beta subunits have no essential regulatory role at the onset or continuance of the voltage-dependent facilitation.
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Lee et al. (2001) studied this question.
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