Recombinant annexin A6 promotes membrane repair and protects against muscle injury
Alexis R. Demonbreun, … , David Y. Barefield, Elizabeth M. McNally
Alexis R. Demonbreun, … , David Y. Barefield, Elizabeth M. McNally
Published November 1, 2019; First published September 23, 2019
Citation Information: J Clin Invest. 2019;129(11):4657-4670. https://doi.org/10.1172/JCI128840.
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Research Article Muscle biology Therapeutics

Recombinant annexin A6 promotes membrane repair and protects against muscle injury

Abstract

Membrane repair is essential to cell survival. In skeletal muscle, injury often associates with plasma membrane disruption. Additionally, muscular dystrophy is linked to mutations in genes that produce fragile membranes or reduce membrane repair. Methods to enhance repair and reduce susceptibility to injury could benefit muscle in both acute and chronic injury settings. Annexins are a family of membrane-associated Ca2+-binding proteins implicated in repair, and annexin A6 was previously identified as a genetic modifier of muscle injury and disease. Annexin A6 forms the repair cap over the site of membrane disruption. To elucidate how annexins facilitate repair, we visualized annexin cap formation during injury. We found that annexin cap size positively correlated with increasing Ca2+ concentrations. We also found that annexin overexpression promoted external blebs enriched in Ca2+ and correlated with a reduction of intracellular Ca2+ at the injury site. Annexin A6 overexpression reduced membrane injury, consistent with enhanced repair. Treatment with recombinant annexin A6 protected against acute muscle injury in vitro and in vivo. Moreover, administration of recombinant annexin A6 in a model of muscular dystrophy reduced serum creatinine kinase, a biomarker of disease. These data identify annexins as mediators of membrane-associated Ca2+ release during membrane repair and annexin A6 as a therapeutic target to enhance membrane repair capacity.

Authors

Alexis R. Demonbreun, Katherine S. Fallon, Claire C. Oosterbaan, Elena Bogdanovic, James L. Warner, Jordan J. Sell, Patrick G. Page, Mattia Quattrocelli, David Y. Barefield, Elizabeth M. McNally

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Figure 9

Recombinant annexin A6 protected against muscle damage in a mouse model of muscular dystrophy in vivo.

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Recombinant annexin A6 protected against muscle damage in a mouse model ...
(A and B) Sgcg-null mice, a model of limb girdle muscular dystrophy 2C, were injected intravenously with recombinant human annexin A6 (rANXA6) or BSA control solution 5 times over 48 hours. Prior to injections, serum creatine kinase (CK) was measured. Two hours after the fifth injection, mice were subjected to 60 minutes of downhill running. Thirty minutes after exercise, serum CK was measured. The fold change in CK after/before running was significantly reduced with rANXA6 administration compared with BSA-injected controls, consistent with a reduction in muscle injury from acute running. (C and D) Sgcg-null mice were injected intravenously every 3 days over 14 days with rANXA6 or control. On day 14, serum CK was evaluated. Serum CK in Sgcg-null mice treated with rANXA6 was lower than PBS control. (E) Sgcg-null mice were injected intravenously every 3 days for 14 days with rANXA6 or recombinant annexin A2. The serum CK fold change after/before treatment (day 14/day 0) was significantly reduced in Sgcg-null mice treated with recombinant annexin A6 compared with annexin A2. (F) Histological analysis of gastrocnemius/soleus muscles from Sgcg-null mice shown in part D injected with PBS or recombinant annexin A6. Low magnification is on the left and high magnification of boxed areas is on the right. Scale bars: 500 μm (left) and 50 μm (right). Data are expressed as mean ± SEM. Differences were assessed by 2-tailed t test (B and E). *P < 0.05 (n = 3 mice per condition, except part D, in which n = 2 WT controls, 1 Sgcg-null control, and 2 Sgcg-null treated mice).