Analysis concerning the influence of dysferlin-deficiency on store-operated calcium entry (SOCE) and triad-associated proteins in murine skeletal muscle

Dysferlinopathien bilden eine Gruppe progressiver Muskelerkrankungen, deren Pathogenese bisher nur unzureichend verstanden ist. Verglichen mit anderen Muskeldystrophien ist eine Besonderheit der Dysferlinopathien eine normale bis überdurchschnittliche Sportlichkeit der betroffenen Patienten, bevor es zum Auftreten von klinischen Symptomen kommt. Diese Merkmale lassen Unterschiede hinsichtlich der Pathogenese vermuten. Anhand der in dieser Arbeit durchgeführten Kalziummessungen von Mausmuskelzellen am Epifluoreszenzmikroskop wurde der Mechanismus des speichergesteuerten, transsarkolemmalen Kalziumeinstroms (SOCE) bei dysferlindefizienten Mäusen detailliert untersucht. Es zeigte sich kein pathologisch erhöhter Kalziumeinstrom in jungen dysferlindefiziente Muskelzellen verglichen zu Wildtyp-Muskelzellen. Zudem wurde eine Vielzahl von Proteinen mittels quantitativer real time PCR (qPCR) und Immunfluoreszenz-Untersuchungen analysiert. Die Ergebnisse dieser Arbeit zeigten, dass STIM1 und Junctophilin1, signifikant im Vergleich zu Wildtyp-Muskelzellen vermindert sind.Dysferlinopathies constitute a group of progressive muscle diseases, whose pathogenesis is not entirely understood. Compared to other muscular dystrophies, a distinctive clinical feature of the Dysferlinopathies is the average to above-average athleticism that patients show prior to clinical symptoms. These characteristics indicate that there are differences regarding the pathogenesis. In this study the mechanism of store-operated calcium entry (SOCE) in dysferlin-deficient murine skeletal muscle was examined by means of calcium measurements using an epifluorescence microscope. Results showed that there is no pathologically increased calcium-influx in dysferlin-deficient murine skeletal muscles compared to wild-type controls. Further, numerous triad-associated proteins were measured by means of quantitative PCR and immunofluorescence. Results showed that in dysferlin-deficient skeletal-muscle STIM1 and Junctophilin1 were significantly reduced compared to wild-type muscle.2021-12-0

Dysferlin mediates membrane tubulation and links T-tubule biogenesis to muscular dystrophy

The multi-C2 domain protein dysferlin localizes to the plasma membrane and the T-tubule system in skeletal muscle; however, its physiological mode of action is unknown. Mutations in the DYSF gene lead to autosomal recessive limb-girdle muscular dystrophy type 2B and Miyoshi myopathy. Here, we show that dysferlin has membrane tubulating capacity and that it shapes the T-tubule system. Dysferlin tubulates liposomes, generates a T-tubule-like membrane system in non-muscle cells, and links the recruitment of phosphatidylinositol 4,5-bisphosphate to the biogenesis of the T-tubule system. Pathogenic mutant forms interfere with all of these functions, indicating that muscular wasting and dystrophy are caused by the dysferlin mutants' inability to form a functional T-tubule membrane system