Age- & Muscle-specific Patterns of Dysferlin Expression in Rats Suggest Role in Injury Response

Background: Muscle cells employ a robust membrane injury response to maintain cell homeostasis, prevent muscle degeneration and minimize fibrosis (1-3). One protein often listed as a key element in this response is dysferlin (4, 5). More recently, it has been suggested that a primary, if not greater, role for dysterlin in muscle is the maintenance of skeletal muscle excitation-contraction coupling (E-CC). We have previously reported that aged gastrocnemius muscle exhibits increased content of dysferlin (6), suggesting it reflected a response to more frequent or long-lasting sarcolemmal membrane stress in old age. We have further reported an age-related loss of sarcoplasmic reticulum (SR) Ca 2+ release in gastrocnemius, but not the soleus (7). Accordingly, we evaluated dysferlin in the soleus and extensor digitorum longus (EDL) muscles of adult and aged, male and female rats (n = 6-8 per group). As dysferlin is known to act in concert with Tripartite motif-containing protein 72 (TRIM72/MG53) to repair membrane disruption in response to injury (8), we evaluated this protein in the same muscles. We hypothesized that, if injury response was the main role of dysferlin, greater dysferlin would be found in the weightbearing soleus vs. EDL muscle and in aged vs. adult rats, regardless of muscle. For this case, we also predicted that dysferlin and TRIM72/MG53 would change in similar fashion across ages and muscles. Conversely, if E-CC maintenance were the principle role of dysteferlin, then we predicted that the protein would be more abundant in the EDL vs. soleus. Methods: Soleus and EDL muscle were harvested from adult (Ad, 6-8 mo.) and aged (Ag, 75% lifespan) male (M) and female (F) F344/BN rats. Immunoblotting was used to assess dysferlin and TRIM72/MG53 abundance in the muscles. SR Ca 2+ release and uptake were determined in both muscles in crude homogenates. Group comparisons were made via 2 x 2 x 2 (age x sex x muscle) ANOVA, with muscle as a repeated factor. A 2 x 2 ANOVA was used to assess body and muscle mass across age and sex. Results: Dysferlin and TRIM72/MG53 were both significantly (P>0.001) higher in the soleus vs. the EDL. A significant effect of age was observed for dysferlin (P = 0.024) and TRIM72/MG53 (P = 0.049). A significant Age x Sex x Muscle (P = 0.036) was observed for TRIM72/MG53, such that the protein was more abundant in greater in aged vs. adult females in the soleus and aged vs. adult males in the EDL. SR Ca 2+ uptake and release were significantly (P < 0.001) higher in the EDL vs. soleus. No effects of age or sex were observed for SR Ca 2+ uptake in either muscle, but a significant sex X muscle interaction (P = 0.033) was found for Ca 2+ release in the EDL. Conclusions: These data are consistent with dysferlin (and TRIM72/MG53) having a primary role in injury response. While the findings do not definitively rule out a role for the proteins in E-CC, the present data suggest it would be a secondary role. References 1.Chakrabarti S, Kobayashi KS, Flavell RA, Marks CB, Miyake K, Liston DR, et al. I J Cell Biol. 2003;162(4):543-9. 2.Wang X, Xie W, Zhang Y, Lin P, Han L, Han P, et al. Cardioprotection of ischemia/reperfusion injury by cholesterol-dependent MG53-mediated membrane repair. Circ Res. 2010;107(1):76-83. 3.Rader EP, Turk R, Willer T, Beltran D, Inamori K, Peterson TA, et al. Proc Natl Acad Sci U S A. 2016;113(39):10992-7. 4.Bansal D, Miyake K, Vogel SS, Groh S, Chen CC, Williamson R, et al. Nature. 2003;423(6936):168-72. 5.Roche JA, Lovering RM, Bloch RJ. Neuroreport. 2008;19(16):1579-84. 6.Russ DW, Krause J, Wills A, Arreguin R. Biogerontology. 2012;13(5):547-55. 7.Russ DW, Grandy JS, Toma K, Ward CW. Acta Physiol (Oxf). 2011; 201(3): 391-403. 8.Quinn CJ, Cartwright EJ, Trafford AW, Dibb KM. J Physiol. 2024;602(9):1893-910. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.