In skeletal muscle, the triad is a structure comprising a transverse (T)-tubule and sarcoplasmic reticulum (SR) cisternae. Triads constitute the basis of excitation–contraction coupling as the cradle of the Ca2+ release complex. We have shown previously that triadin, a member of this complex, has shaping properties on reticulum membrane and is indirectly involved in a link between triads and microtubules. We have identified here that CLIMP-63 (also known as CKAP4), as the partner of triadin, is responsible for this association of triads and microtubules. Triadin and CLIMP-63 interact through their respective luminal domains and the shaping properties of triadin depend on the capacity of CLIMP-63 to bind microtubules with its cytosolic portion. In skeletal muscle, CLIMP-63 is localized in the SR, including triads, and is associated with the Ca2+ release complex through its interaction with triadin. Knockout of triadin in muscles results in the delocalization of CLIMP-63 from triads, its dissociation from the Ca2+ release complex and a disorganization of the microtubule network. Our results suggest that the association of triadin and CLIMP-63 could be involved in the shaping of SR terminal cisternae and in the guidance of microtubules close to the triads.
The authors declare no competing or financial interests.
Conceptualization: A.F.-L., I.M., J.F.; Methodology and Investigation: A.O., M.S., O.S., M.B., Y.C.; Proteomic analysis: M.B., Y.C.; Formal analysis: A.O., M.S., A.F.-L., I.M.; Writing – original draft preparation: A.F.-L., I.M.; Writing – review and editing: A.F.-L., I.M., J.F., Y.C., A.O., M.S.; Funding acquisition: I.M., Y.C.; Supervision: I.M., A.F.-L.
This work was supported by grants from the Institut National de la Santé et de la Recherche Médicale (INSERM), the Association Française contre les Myopathies (AFM), and the Foundation Daniel Ducoin. Proteomic experiments were partly supported by the Agence Nationale de la Recherche (Investissement d'Avenir Infrastructures, ProFi project) [grant number ANR-10-INBS-08-01].
Supplementary information available online at http://jcs.biologists.org/lookup/doi/10.1242/jcs.188862.supplemental
- Received March 3, 2016.
- Accepted August 18, 2016.
- © 2016. Published by The Company of Biologists Ltd