New Tools For Activation Of Src Family Isoforms In Vivo Demonstrate Specific Roles For Each Isoform In Cell Motility

The Src family kinases (SFK) include nine highly homologous members. To identify unique functions for individual SFKs, we have inserted an engineered FKBP domain into a conserved region of the kinases’ catalytic domain, generating rapamycin-regulated (RapR) analogs1 of Src, Lyn, Yes and Fyn, enabling each isoform to be activated specifically and independently in living cells. The cellular morphodynamics and corresponding subcellular translocation induced by activation of each isoform were characterized using new computational methods, revealing distinct roles for each isoform. While both Src and Fyn activation initially induced spreading, only for Src this was followed by polarized movement. Activation of Src led to kinase redistribution from the perinulcear region to the cell periphery, while Fyn remained uniformly distributed throughout the observation period. Changes in the lipidation or swapping the effector binding domains of each isoform interconverted the cell behaviors and corresponding translocation dynamics. Differences in focal adhesion dynamics driven by Src versus Fyn activation provide a mechanistic model for the distinct morphological changes induced by each kinase.