Mac-chanosensing: an in vivo study of how substrate stiffness regulates macropinocytosis during macrophage migration (360G-Wellcome-224063_Z_21_Z)

Macropinocytosis is an evolutionarily conserved yet ill-studied endocytic process. It is characterised by the formation of Rac1-actin-dependent membrane ruffles and shares the same core machinery with the process of cell migration. Macropinocytosis can be utilised by professional antigen-presenting cells like macrophages to sample their surrounding environments for signs of infection or by cancer cells to fuel their proliferation. Despite its important roles in many pathophysiological conditions, factors that regulate macropinocytosis remain largely unclear. Traditionally, it is believed that growth factors play a central role in triggering macropinocytosis. However, recent in vitro evidence suggests physical cues such as hydraulic pressure and membrane tension also significantly impact this process. Nevertheless, an in vivo model that intercalates physical factors in the regulation of macropinocytosis is still lacking. This proposal looks at the highly macropinocytic macrophages and aims to combine the advantage of the mechanically tunable Xenopus embryos with the high-resolution imaging capability of zebrafish embryos and larvae to address three key questions: - Can tissue mechanical properties affect the migration and macropinocytosis of macrophages? - Establishing a Xenopus ex vivo primitive myeloid-derived macrophage model for macropinocytosis study. - Can substrate stiffness affect bacterial clearance by macrophages during wounding and inflammation? Keywords: Macropinocytosis, mechanosensing, macrophages, Xenopus, zebrafish.