Structural Basis for the Distinct Membrane Binding Activity of the Homologous C2A Domains of Myoferlin and Dysferlin

Abstract

Dysferlin has been implicated in acute membrane repair processes, whereas myoferlin's activity is maximal during the myoblast fusion stage of early skeletal muscle cell development. Both proteins are similar in size and domain structure; however, despite the overall similarity, myoferlin's known physiological functions do not overlap with those of dysferlin. Here we present for the first time the X-ray crystal structure of human myoferlin C2A to 1.9 Å resolution bound to two divalent cations, and compare its 3D structure and membrane binding activities to that of dysferlin C2A. We find that while dysferlin C2A binds membranes in a Ca 2+ -dependent manner, Ca 2+ -binding was the rate-limiting kinetic step for this interaction. Myoferlin C2A, on the other hand, binds two calcium ions with an affinity 3-fold lower than that of dysferlin C2A; and, surprisingly, myoferlin C2A binds only marginally to phospholipid mixtures with a high fraction of phosphatidylserine.

The Dystrophin Node as Integrator of Cytoskeletal Organization, Lateral Force Transmission, Fiber Stability and Cellular Signaling in Skeletal Muscle

“…Freeze-fracture electron microscopy has established that the number and structure of caveolae are changed in dystrophinopathy, suggesting an important role of abnormal cavins in muscular dystrophy [ 39 , 117 ]. Of note, the crucial repair protein myoferlin [ 118 ] is also closely associated with caveolin and intrinsically involved in the maintenance and structural integrity of the sarcolemmal membrane, together with the Ca 2+ -dependent repair protein dysferlin [ 119 ].…”

The Many Faces of DFNB9: Relating OTOF Variants to Hearing Impairment

“…However, despite laborious efforts from several research groups, this has not been the case for other C 2 domains so far, presumably because higher protein dynamics prevent the forming of crystals. Notably, the same seems to be true for the myoferlin and dysferlin C 2 domains, of which only the structures of the C 2 A domains could be resolved to date [ 61 ]. Whether the high flexibility of the ferlin C 2 B-C 2 F domains is a biological defect or a feature relevant for proper function remains to be determined.…”

Ferlin Overview: From Membrane to Cancer Biology

“…A recent publication confirmed that myoferlin and dysferlin C2A domains exhibit different Ca 2+ affinities. However, they describe myoferlin C2A domain with a lower Ca 2+ affinity than the dysferlin homolog C2 domain, and a marginal binding of myoferlin C2A domain to phospholipid mixture containing PS [33]. The binding of dysferlin C2A to PS was confirmed and extended to several phosphoinositide monophosphates in a Ca 2+ -dependent fashion.…”