Effect of Pathogenic Mutations on the Formation of High-Order Dynamin 2 Assemblies in Living Cells

Mutations in dynamin 2 (DNM2) have been associated with two distinct movement disorders: Charcot-Marie-Tooth neuropathies (CMT) and centronuclear myopathy (CNM). Most of these mutations are clustered in the pleckstrin homology domain (PHD), which engages in intramolecular interactions that limit dynamin self-assembly and GTPase activation. CNM mutations interfere with these intramolecular interactions and suppress the formation of the autoinhibited state. CMT mutations are located primarily on the opposite surface of the PHD, which is specialized for phosphoinositide binding. It has been speculated that the distinct locations and interactions of residues mutated in CMT and CNM explain why each set of mutations causes either one disease or the other, despite their close proximity within the PHD sequence. We previously reported that at least one CMT-causing mutant, lacking residues ₅₅₅DEE₅₅₇ (ΔDEE), displays the same inability to undergo autoinhibition as observed in CNM-linked mutants. Here, we show that both the DNM2^ΔDEE and CNM-linked DNM2^A618T mutants form larger and more stable structures on the plasma membrane than that of wild-type DNM2 (DNM2^WT). However, DNM2^A618T forms cytoplasmic inclusions at concentrations lower than those of either DNM2^WT or DNM2^ΔDEE, suggesting that CNM-linked mutations confer more severe gain-of-function properties than the ΔDEE mutation.