Role of the Non-Receptor Tyrosine Kinase ACK2 in EGF Receptor Degradation
Abstract
Epidermal growth factor receptor (ErbB-1) and members of the ErbB family of receptor tyrosine kinases have been implicated in several mitogenic signaling pathways. Regulated growth factor-mediated signaling relies upon a balance between receptor activation, endocytosis, and degradation. As a result, overexpression or mutations altering receptor kinase activity disrupts this delicate balance, and is often sufficient to cause malignant transformation of the cell. We are particularly interested in the emerging role of the nonreceptor tyrosine kinase, ACK2, and its substrate, SH3PX1, in regulating the degradation of ErbB-2 family members. Establishing a role for ACK2 and SH3PX1 in ErbB-2 receptor degradation is especially appealing based on the predictive property between receptor overexpression and breast cancer. Currently, we are interested in further characterizing the ACK2-SH3PX1 interaction and determining the significance of ACK2-dependent phosphorylation of SH3PX1 in cells. To address these objectives, we have carried out deletion analysis studies to delineate the region of the phosphorylation site(s) on SH3PX1. In our studies, we have demonstrated that the phosphorylation signal of SH3PX1 is lost in the C-terminal truncation mutant DeltaC393. In parallel site-directed mutagenesis studies, we conclude that all conserved point-mutants of SH3PX1 retain a phosphorylation signal comparable to wild-type. At this point, we believe that Mass Spectrometry may provide a more sensitive means to identify the ACK2 phsophorylation site on SH3PX1. Currently, efforts to generate recombinant forms of ACK2 and SH3PX1 are underway to aid in phosphopeptide mapping experiments, as well as screens for ACK2 inhibitors. The ability to regulate this phosphorylation event, perhaps through the identification of a dominant-negative form of SH3PX1, or specific inhibitors of ACK2, will help determine the importance of ACK2 activity in receptor endocytosis and degradation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2004
- Accession Number
- ADA427754
Entities
People
- Carrie Stearns
Organizations
- Cornell University