The PtdIns3P phosphatase myotubularin is a cytoplasmic protein that also localizes to Rac1-inducible plasma membrane ruffles.
Myotubularin, the phosphatase mutated in X-linked myotubular myopathy, was shown to dephosphorylate phosphatidylinositol 3-monophosphate (PtdIns3P) and was also reported to interact with nuclear transcriptional regulators from the trithorax family. We have characterized a panel of specific antibodies and investigated the subcellular localization of myotubularin. Myotubularin is not detected in the nucleus, and localizes mostly as a dense cytoplasmic network. Overexpression of myotubularin does not detectably affect vesicle trafficking in the mammalian cells investigated, in contrast to previous observations in yeast models. Both mutation of a key aspartate residue of myotubularin and dominant activation of Rac1 GTPase lead to the recruitment of myotubularin to specific plasma membrane domains. Localization to Rac1-induced ruffles is dependent on the presence of a domain highly conserved in the myotubularin family (that we named RID). We thus propose that myotubularin may dephosphorylate a subpool of PtdIns3P (or another related substrate) at the plasma membrane.
Laporte
Jocelyn
J
Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, 1 rue Laurent Fries, BP 10142, 67404 Illkirch Cedex, CU de Strasbourg, France. mtm@titius.u-strasbg.fr
Blondeau
Francois
F
Gansmuller
Anne
A
Lutz
Yves
Y
Vonesch
Jean-Luc
JL
Mandel
Jean-Louis
JL
D000818:Animals; D000906:Antibodies; D002451:Cell Compartmentation / Q000235:genetics; D022081:Cell Surface Extensions / Q000201:enzymology* / Q000648:ultrastructure; D003593:Cytoplasm / Q000201:enzymology*; D022162:Cytoplasmic Vesicles / Q000378:metabolism / Q000648:ultrastructure; D005057:Eukaryotic Cells / Q000201:enzymology* / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018613:Microscopy, Confocal; D009154:Mutation / Q000235:genetics; D020914:Myopathies, Structural, Congenital / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D017027:Protein Tyrosine Phosphatases / Q000172:deficiency* / Q000235:genetics; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D000906:Antibodies; D018129:Phosphatidylinositol Phosphates; D017027:Protein Tyrosine Phosphatases; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C099588:myotubularin; D020830:rac1 GTP-Binding Protein