WANTED – Dead or alive: Myotubularins, a large disease-associated protein family

Matthieu Raess (UMR7156, IGBMC), Sylvie Friant (UMR7156), Belinda S. Cowling (IGBMC), Jocelyn Laporte (IGBMC).

Myotubularins define a large family of proteins conserved through evolution. Several members are mutated in different neuromuscular diseases including centronuclear myopathies and Charcot-Marie-Tooth (CMT) neuropathies, or are linked to a predisposition to obesity and cancer. While some members have phosphatase activity against the 3-phosphate of phosphoinositides, regulating the phosphorylation status of PtdIns3P and PtdIns(3,5)P₂ implicated in membrane trafficking and autophagy, others lack key residues in the catalytic site and are classified as dead-phosphatases. However, these dead phosphatases regulate phosphoinositide-dependent cellular pathways by binding to catalytically active myotubularins. Here we review previous studies on the molecular regulation and physiological roles of myotubularins. We also used the recent myotubularins three-dimensional structures to underline key residues that are mutated in neuromuscular diseases and required for enzymatic activity and/or regulation. In addition, through database mining and analysis, expression profile and specific isoforms of the different myotubularins are described in depth, as well as a revisited interaction network. Comparison of the interactome and expression data for each myotubularin highlights specific protein complexes and tissues where myotubularins should have a key regulatory role.