In Vivo Structure-Function Studies on the Precise Role of ErbB-2 Signaling in Mammary Gland Development

摘要

The ErbB2 receptor tyronsine kinase plays important roles in development and disease. To investigate the developmental roles of ErbB2 mediated signaling in vivo, we have generated a series of erbB2 cDNA knock-in animals expressing different ErbB2 mutants under the transcriptional control of the endogenous promoter. Firstly, we showed that the kinase activity of ErbB2 is essential for embryonic development since this mutant is a phenocopy of the ERBB2 null mutants, which die at midgestation with cardiac and peripheral nervous system defects. In our studies, we also established a minimal threshold level of ErbB2 that was required for embryonic development and survival. The tyrosone autophosphorylation site YlO28 mediated a negative regulatory signal that affected the level of ErbB2 proteins expressed. This tyronsine appears to play a role in normal signaling and development. The mechanism of action is known at this point, however, the downregulatory effect is independent of Cbl binding and ubiquitylation of the receptor. In fact, we have also identified the phosphorylation sites in ErbB2 that is required for it's interaction with Cbl, although ErbB2 appears to be refractory to the downregulatory effect of Cbl. The results of my studies will provide important insight into the regulatory mechanisms controlling ErbB2 signaling and may lead to improved therapeutics.