How filopodia form (360G-Wellcome-219482_Z_19_Z)

Filopodia are finger-like actin rich projections from cells that are ubiquitously present during cell movement, are involved in cell connectivity, and are hijacked for internalization by pathogens. We established a cell-free system of filopodia-like structure formation using supported lipid bilayers and frog egg extracts, which has generated hypotheses about where and when filopodia form. My first aim is to discover how endocytosis and phosphoinositide lipid metabolism contribute to the time and place of filopodia formation and suppression in retinal ganglion cell neurons. We will examine the timing and contributions of neurotrophic factor signalling through PI(4,5)P2, PI(3,4,5)P3, PI(3,4)P2 and PI(3)P to membrane deformation and filopodial protrusion. We will explore filopodia in axon guidance, terminal arborization and synaptogenesis, and recovery from neuronal injury. My second aim is to identify the proteins needed for formation of filopodia-like structures to increase our understanding of the molecular mechanisms that determine filopodia function in cells. Where filopodia form determines the direction of cell movement, their length determines the extent of signal sensitivity and their lifetime determines the strength of signaling or duration of migration and adhesion. Our molecular and cellular studies may also give us information needed to manipulate actin regulation therapeutically.