Desmin interacts with STIM1 and coordinates Ca2+ signaling in skeletal muscle
Hengtao Zhang, Victoria Graham Bryson, Chaojian Wang, TianYu Li, Jaclyn P. Kerr, Rebecca Wilson, Deborah M. Muoio, Robert J. Bloch, Christopher Ward, Paul B. Rosenberg
Hengtao Zhang, Victoria Graham Bryson, Chaojian Wang, TianYu Li, Jaclyn P. Kerr, Rebecca Wilson, Deborah M. Muoio, Robert J. Bloch, Christopher Ward, Paul B. Rosenberg
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Research Article Muscle biology

Desmin interacts with STIM1 and coordinates Ca2+ signaling in skeletal muscle

Abstract

Stromal interaction molecule 1 (STIM1), the sarcoplasmic reticulum (SR) transmembrane protein, activates store-operated Ca2+ entry (SOCE) in skeletal muscle and, thereby, coordinates Ca2+ homeostasis, Ca2+-dependent gene expression, and contractility. STIM1 occupies space in the junctional SR membrane of the triads and the longitudinal SR at the Z-line. How STIM1 is organized and is retained in these specific subdomains of the SR is unclear. Here, we identified desmin, the major type III intermediate filament protein in muscle, as a binding partner for STIM1 based on a yeast 2-hybrid screen. Validation of the desmin-STIM1 interaction by immunoprecipitation and immunolocalization confirmed that the CC1-SOAR domains of STIM1 interact with desmin to enhance STIM1 oligomerization yet limit SOCE. Based on our studies of desmin-KO mice, we developed a model wherein desmin connected STIM1 at the Z-line in order to regulate the efficiency of Ca2+ refilling of the SR. Taken together, these studies showed that desmin-STIM1 assembles a cytoskeletal-SR connection that is important for Ca2+ signaling in skeletal muscle.

Authors

Hengtao Zhang, Victoria Graham Bryson, Chaojian Wang, TianYu Li, Jaclyn P. Kerr, Rebecca Wilson, Deborah M. Muoio, Robert J. Bloch, Christopher Ward, Paul B. Rosenberg

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Figure 6

Desmin KO muscle fibers exhibit altered Ca2+ signaling.

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Desmin KO muscle fibers exhibit altered Ca2+ signaling. (A) Mn2+quench a...
(A) Mn2+quench assay to compare SOCE in WT and DES-KO fibers. Fura-2 loaded WT (black) and DES-KO (red) FDB muscle fibers were imaged using 360 nm excitation, the isosbestic point for Fura-2. (B) The initial rates of Mn2+ quenching fluorescence were defined as SOCE, calculated and summarized in the Methods section. (C and D) Fura-4F loaded muscle fibers for WT (black) and DES-KO (red) subjected to SR Ca2+ depletion by 10 mM caffeine in the presence of 30 μM CPA. Summarized data for SR store Ca2+ content from WT (open column, n = 8) and DES-KO (filled red column, n = 7) FDB fibers. Significance is indicated by P < 0.05. (E and F) Representative FRET traces for D1ER, a genetically encoded SR Ca2+ indicator, electroporated into the FDB muscles. Ca2+ release was compared for WT (top) and DES-KO (bottom) fibers electroporated with D1ER in response to 30 mM caffeine and uptake of Ca2+ by SERCA. Quantification of basal Ca2+ level at resting state (F), SR Ca2+ content defined as Ca2+ release by 30 mM caffeine (G), and SR Ca2+ uptake measured as initial slope after reintroduction of 2 mM Ca2+ in WT (black column, n = 98) and DES-KO (red column, n = 52) FDB fibers (H). *P < 0.05; **P < 0.001.