DEPENDENCE ON THE MOTIF YIPP FOR THE PHYSICAL ASSOCIATION OF JAK2 KINASE WITH THE INTRACELLULAR CARBOXYL TAIL OF THE ANGIOTENSIN-II AT(1) RECEPTOR

Angiotensin II is the effector molecule of the renin-angiotensin syste m. Virtually all of its biochemical actions are mediated through a sin gle class of cell-surface receptors called AT(1). These receptors cont ain the structural features of the seven-transmembrane, G-protein-coup led receptor superfamily. Angiotensin II, acting through the AT(1) rec eptor, also stimulates the Jak/STAT pathway by inducing ligand-depende nt Jak2 tyrosine phosphorylation and activation. Here, we show that a glutathione S-transferase fusion protein containing the carboxyl-termi nal 54 amino acids of the rat AT(1A) receptor physically binds to Jak2 in an angiotensin II-dependent manner. Deletional analysis, using bot h in vitro protocols and cell transfection analysis, showed that this association is dependent on the AT(1A) receptor motif YIPP (amino acid s 319-322), The mild-type AT(1A) receptor can induce Jak2 tyrosine pho sphorylation, In contrast, an AT(1A) receptor lacking the YIPP motif i s unable to induce ligand-dependent phosphorylation of Jak2. Competiti on experiments with synthetic peptides suggest that each of the YIPP a mino acids, including tyrosine 319, is important in Jak2 binding to th e AT(1A) receptor. The binding of the AT(1A) receptor to the intracell ular tyrosine kinase Jak2 supports the concept that the seven-transmem brane superfamily of receptors can physically associate with enzymatic ally active intracellular proteins, creating a signaling complex mecha nistically similar to that observed with growth factor and cytokine re ceptors.