The formation of filopodia in Metazoa and Amoebozoa requires the activity of myosin 10 (Myo10) in mammalian cells and of Dictyostelium unconventional myosin 7 (DdMyo7) in the social amoeba Dictyoste-lium. However, the exact roles of these MyTH4-FERM myosins (myosin tail homology 4-band 4.1, ezrin, radixin, moesin; MF) in the initiation and elongation of filopodia are not well defined and may reflect conserved functions among phylogenetically diverse MF myosins. Phylogenetic analysis of MF myosin domains suggests that a single ancestral MF myosin existed with a structure similar to DdMyo7, which has two MF domains, and that subsequent duplications in the metazoan lineage produced its functional homolog Myo10. The essential functional features of the DdMyo7 myosin were identified using quantitative live-cell imaging to characterize the ability of various mutants to rescue filopod formation in myo7-null cells. The two MF domains were found to function redundantly in filopod formation with the C-terminal FERM domain regulating both the number of filopodia and their elongation velocity. DdMyo7 mutants consisting solely of the motor plus a single MyTH4 domain were found to be capable of rescuing the formation of filopodia, establishing the minimal elements necessary for the function of this myosin. Interestingly, a chimeric myosin with the Myo10 MF domain fused to the DdMyo7 motor also was capable of rescuing filopod formation in the myo7-null mutant, supporting fundamental functional conservation between these two distant myosins. Together, these findings reveal that MF myosins have an ancient and conserved role in filopod formation.
|Original language||English (US)|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Dec 13 2016|
Bibliographical noteFunding Information:
We thank Hilary Bauer, Zo? Henrot, and Alex McQuown and Drs. Guillermo Marqu?s and Mark Sanders (University of Minnesota Imaging Centers) for expert technical assistance; Drs. Naomi Courtemanche, Melissa Gardner, Sivaraj Sivaramakrishnan, and Gaku Ashiba for many valuable discussions; Dr. Martin Kollmar for developing and maintaining CyMoBase (cymobase.org); Dr. Tandy Warnow (University of Illinois) for introducing us to SAT?; and the Minnesota Supercomputing Institute for providing excellent computational resources. K.J.P. was supported by NIH Training Program in Muscle Research Grant AR007612 and a University of Minnesota Doctoral Dissertation Fellowship; H.V.G. was supported by National Science Foundation (NSF) Award MCB-1244593; G.W.G.L. was supported by NIH Awards R42DA037622 and R21NS095109-01; A.H. was supported by grants from the ANR-13-BSV8-0019-01, Ligue Nationale Contre le Cancer, and Association pour la Recherche sur le Cancer Subvention Fixe; and M.A.T. was supported by NSF Grant MCB-124423.
- Cell motility