Author + information
- Received January 14, 2016
- Revision received February 23, 2016
- Accepted February 23, 2016
- Published online April 25, 2016.
- Kurt W. Prins, MD, PhDa,
- Michelle L. Asp, PhDb,
- Huiliang Zhang, PhDc,
- Wang Wang, MD, PhDc and
- Joseph M. Metzger, PhDb,∗ ()
- aCardiovascular Division, University of Minnesota Medical School, Minneapolis, Minnesota
- bDepartment of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota
- cMitochondria and Metabolism Center, University of Washington, Seattle, Washington
- ↵∗Reprint requests and correspondence:
Dr. Joseph M. Metzger, Department of Integrative Biology and Physiology, University of Minnesota, 321 Church Street SE, Minneapolis, Minnesota 55455.
• Decreased junctophilin-2 levels are associated with cardiac t-tubule derangements in mdx mice, the mouse model of Duchenne muscular dystrophy (DMD).
• Reduced junctophilin-2 protein levels correlate with increases in total microtubule content in mdx hearts.
• Colchicine-mediated microtubule depolymerization increases junctophilin-2 protein levels and improves localization patterns which, in turn, are associated with t-tubule reorganization and reduced calcium sparks.
• This study identifies microtubule-mediated misregulation of junctophilin-2 as a novel molecular mechanism in Duchenne cardiomyopathy.
Cardiac myocytes from the mdx mouse, the mouse model of Duchenne muscular dystrophy, exhibit t-tubule disarray and increased calcium sparks, but a unifying molecular mechanism has not been elucidated. Recently, improper trafficking of junctophilin (JPH)-2 on an altered microtubule network caused t-tubule derangements and calcium mishandling in a pressure-overload heart failure model. Mdx cardiac myocytes have microtubule abnormalities, but how this may affect JPH-2, t-tubules, and calcium handling has not been established. Here, we investigated the hypothesis that an inverse relationship between microtubules and JPH-2 underlies t-tubule disruptions and calcium mishandling in mdx cardiac myocytes. Confocal microscopy revealed t-tubule disorganization in mdx cardiac myocytes. Quantitative Western blot analysis demonstrated JPH-2 was decreased by 75% and showed an inverse hyperbolic relationship with α- and β-tubulin, the individual components of microtubules, in mdx hearts. Colchicine-induced microtubule depolymerization normalized JPH-2 protein levels and localization, corrected t-tubule architecture, and reduced calcium sparks. In summary, these results suggest microtubule-mediated misregulation of JPH-2 causes t-tubule derangements and altered calcium handling in mdx cardiac myocytes.
This work was supported by the University of Minnesota Lillehei Heart Institute.
Dr. Metzger has received grants from the National Institutes of Health (NIH) and MDA. Dr. Prins has received NIH T32 (HL069764) and F32 (HL129554) grants. Dr. Asp has received the NIH F32 (HL115876) grant. Dr. Wang has received the NIH RO1 (HL114760) grant. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Received January 14, 2016.
- Revision received February 23, 2016.
- Accepted February 23, 2016.
- The Authors