期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：50
页码：E8059-E8068
DOI：10.1073/pnas.1615392113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceFilopodia are actin-based structures used by cells to sense chemical stimuli and promote adhesion to the extracellular environment during the development of multicellular organisms. Filopod formation in evolutionarily distant organisms requires MyTH4-FERM (myosin tail homology 4-band 4.1, ezrin, radixin, moesin; MF) myosins that consist of a motor domain paired with a tail domain that binds cytoskeletal and membrane proteins. Mutational analysis identified the minimal requirements for MF myosin function in filopod formation and revealed that the key features are conserved between amoebozoan and metazoan MF myosins. These findings have implications for understanding the fundamental principles of how filopodia form and how MF myosins function in phylogenetically distant organisms. 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 Dictyostelium. 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.
