CRK and infection: We predict that this process of recruitment and activation is independent of events that occur during the initial stages of infection (<1 h) where engagement of RTKs like the epidermal growth factor receptor (EGFR) (49), EphrRA2 (50), and platelet-derived growth factor receptor (PDGFR) (35) and/or tyrosine-phosphorylated Tarp may transiently recruit Crk proteins and PI3K to entry sites.