Project Summary/Abstract Filopodia play important roles in a variety of cellular processes including immune response, neuronal pathogenesis, and wound healing. Cells use filopodia to survey their environment and are typically upregulated in motile cells. Filopodia are thin, rod-like cellular protrusions composed of parallel bundles of actin and found in divergent organisms such as the social amoeba Dictyostelium and metazoans. The core mechanisms behind filopodia formation are conserved throughout metazoans and amoebozoans, yet the mechanism of filopodia initiation is still unknown. MyTH4-FERM (MF) myosins, the amoeboid Myosin 7 (DdMyo7) and metazoan Myosin 10 (Myo10), are essential for filopodia initiation. They are targeted to the membrane, form initiation foci, and are subsequently enriched in filopodia tips during elongation. Filopodia initiation is being studied in the simple model organism Dictyostelium because it has minimal protein redundancy, allows for efficient genetic manipulation, and biochemical quantities of material are easily obtained. The ultimate goal of the proposed work is to understand the role of MF myosins during filopodia initiation. To accomplish this, I will 1) define the motor properties of DdMyo7 using standard motility assays and 2) identify DdMyo7 interacting partners using an unbiased proximity ligase screen. The data generated by the proposed experiments will provide critical information needed to understand how a filopodia myosin drives initiation.

Project Narrative Filopodia are protrusions used by cells to probe their environment and aid during mobile processes such as axon guidance, development, and cancer cell metastasis. For example, aggressive cancer cells upregulate filopodia during metastasis to invade other tissues, and ablation of filopodia in cancer cells results in a striking reduction of metastatic potential. The structure of filopodia is well characterized, but how they form is not well understood. An actin based molecular motor is responsible for initiating filopodia, however it is unclear how it accomplishes this feat. Insights from this work will lead to a better understanding of how this motor forms filopodia during highly mobile processes such as cancer cell metastasis.