Molecular Recognition of Endocytic Codes in Receptor Tyrosine Kinases.
Annual rept. 1 Jul 94-30 Jun 96,
CALIFORNIA UNIV SAN DIEGO LA JOLLA
Pagination or Media Count:
Enigma, isolated based on interaction with the human insulin receptor InsR using a yeast two-hybrid system, contains three LIM domains within its carboxyl terminus. The carboxyl LIM domain LIM3 specifically recognizes the endocytic codes of InsR. Interaction of two random peptide libraries indicates the specific binding of Gly-Pro-Hyr-Gly-Pro-Hyr-TyrPhe corresponding to the major endocytic code of InsR. The ability of LIM3 of Enigma to recognize the endocytic codes of InsR fulfills the first property of the endocytic mechanism. In contrast to LIM3 of Enigma binding to InsR, LIM2 of Enigma associates specifically with the tyrosine kinase receptor Ret. Mutational analysis indicated that Tyr586 at the carboxyl terminus of Ret is essential for the Ret and Enigma interaction. Mutations of Retptc2 which fail to interact with Enigma also lose their ability to stimulate mitogenic signaling. Co-expression of LIM domains of Enigma blocked Retptc2 stimulated DNA synthesis, indicating that Enigma is involved in the mitogenic signaling of Ret. These studies have indicated that two LIM domains of Enigma can interact with two receptor tyrosine kinases through tyrosine-based motifs with specificity residing in both the LIM domains and in the target structures.
- Medicine and Medical Research