Fig. 3.

Light-induced activation of PI3K. Grb14, an upstream regulator of IR, requires photobleaching of rhodopsin for membrane targeting. Grb14 protects light-dependent IR activation in rod photoreceptors against dephosphorylation by PTP1B. Our studies suggest that Grb14 translocates to photoreceptor outer segments after photobleaching of rhodopsin and protects IR phosphorylation in rod photoreceptor cells. Light-activated IR is subsequently associated with PI3K, a cell survival factor, and, thus, regulates the downstream survival pathway. R*, photoactivated rhodopsin; Grb14, growth factor receptor-bound protein 14; IR, insulin receptor; PTP1B, protein tyrosine phosphatase; Y-P, phosphotyrosine.