Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Nov;237(11):4197-4214.
doi: 10.1002/jcp.30870. Epub 2022 Sep 26.

STAC3 determines the slow activation kinetics of CaV 1.1 currents and inhibits its voltage-dependent inactivation

Wietske E Tuinte  1 , Enikő Török  1 , Irene Mahlknecht  1 , Petronel Tuluc  2 , Bernhard E Flucher  1 , Marta Campiglio  1
Affiliations

STAC3 determines the slow activation kinetics of CaV 1.1 currents and inhibits its voltage-dependent inactivation

Wietske E Tuinte et al. J Cell Physiol. 2022 Nov.

Abstract

The skeletal muscle CaV 1.1 channel functions as the voltage-sensor of excitation-contraction (EC) coupling. Recently, the adaptor protein STAC3 was found to be essential for both CaV 1.1 functional expression and EC coupling. Interestingly, STAC proteins were also reported to inhibit calcium-dependent inactivation (CDI) of L-type calcium channels (LTCC), an important negative feedback mechanism in calcium signaling. The same could not be demonstrated for CaV 1.1, as STAC3 is required for its functional expression. However, upon strong membrane depolarization, CaV 1.1 conducts calcium currents characterized by very slow kinetics of activation and inactivation. Therefore, we hypothesized that the negligible inactivation observed in CaV 1.1 currents reflects the inhibitory effect of STAC3. Here, we inserted a triple mutation in the linker region of STAC3 (ETLAAA), as the analogous mutation abolished the inhibitory effect of STAC2 on CDI of CaV 1.3 currents. When coexpressed in CaV 1.1/STAC3 double knockout myotubes, the mutant STAC3-ETLAAA failed to colocalize with CaV 1.1 in the sarcoplasmic reticulum/membrane junctions. However, combined patch-clamp and calcium recording experiments revealed that STAC3-ETLAAA supports CaV 1.1 functional expression and EC coupling, although at a reduced extent compared to wild-type STAC3. Importantly, STAC3-ETLAAA coexpression dramatically accelerated the kinetics of activation and inactivation of CaV 1.1 currents, suggesting that STAC3 determines the slow CaV 1.1 currents kinetics. To examine if STAC3 specifically inhibits the CDI of CaV 1.1 currents, we performed patch-clamp recordings using calcium and barium as charge carriers in HEK cells. While CaV 1.1 displayed negligible CDI with STAC3, this did not increase in the presence of STAC3-ETLAAA. On the contrary, our data demonstrate that STAC3 specifically inhibits the voltage-dependent inactivation (VDI) of CaV 1.1 currents. Altogether, these results designate STAC3 as a crucial determinant for the slow activation kinetics of CaV 1.1 currents and implicate STAC proteins as modulators of both components of inactivation of LTCC.

Keywords: L-type voltage-gated calcium channels; calcium-dependent inactivation; current kinetics; excitation−contraction coupling; voltage-dependent inactivation.

PubMed Disclaimer

References

REFERENCES

    1. Ahern, C. A., Powers, P. A., Biddlecome, G. H., Roethe, L., Vallejo, P., Mortenson, L., Strube, C., Campbell, K. P., Coronado, R., & Gregg, R. G. (2001). Modulation of L-type Ca2+ current but not activation of Ca2+ release by the gamma1 subunit of the dihydropyridine receptor of skeletal muscle. BMC Physiology, 1, 8.
    1. Bannister, R. A., & Beam, K. G. (2013). Ca(V)1.1: The atypical prototypical voltage-gated Ca(2)(+) channel. Biochimica et Biophysica Acta/General Subjects, 1828, 1587-1597.
    1. Di Biase, V., Tuluc, P., Campiglio, M., Obermair, G. J., Heine, M., & Flucher, B. E. (2011). Surface traffic of dendritic CaV1.2 calcium channels in hippocampal neurons. Journal of Neuroscience, 31, 13682-13694.
    1. Campiglio, M., Biase, D. I., Tuluc, V. P., & Flucher, B. E. (2013). Stable incorporation versus dynamic exchange of beta subunits in a native Ca2+ channel complex. Journal of Cell Science, 126, 2092-2101.
    1. Campiglio, M., Coste De Bagneaux, P., Ortner, N. J., Tuluc, P., Van Petegem, F., & Flucher, B. E. (2018). STAC proteins associate to the IQ domain of CaV1.2 and inhibit calcium-dependent inactivation. Proceedings of the National Academy of Sciences of the United States of America, 115, 1376-1381.

Publication types

MeSH terms

LinkOut - more resources