Huntingtin-interacting protein 1 phosphorylation by receptor tyrosine kinases

Area of Science:

• Molecular Biology
• Cellular Biology
• Cancer Research

Background:

• Huntingtin-interacting protein 1 (HIP1) interacts with lipids, clathrin, actin, and receptor tyrosine kinases (RTKs).
• HIP1 is overexpressed in various tumors and is a prognostic marker in prostate cancer.
• HIP1 overexpression elevates epidermal growth factor receptor (EGFR) levels and transforms fibroblasts.

Purpose of the Study:

• To investigate the tyrosine phosphorylation of HIP1 by RTKs.
• To identify the specific regions and residues involved in HIP1 phosphorylation.
• To determine the functional consequences of HIP1 phosphorylation on cellular survival.

Main Methods:

• Investigated HIP1 tyrosine phosphorylation in the presence of EGFR, PDGFβR, and their oncogenic derivatives.
• Identified a four-tyrosine HIP1 phosphorylation motif (HPM) in HIP1's N-terminal region.
• Utilized tyrosine-to-phenylalanine point mutations to assess the role of HPM tyrosines.

Main Results:

• HIP1 is tyrosine phosphorylated by EGFR and PDGFβR, but not by H/P and T/P oncoproteins.
• A specific N-terminal HPM is required for EGFR and PDGFβR-mediated phosphorylation.
• A tyrosine residue (Y152) within the HPM inhibits HIP1 tyrosine phosphorylation.
• Mutations in the HPM lead to proapoptotic activity, suggesting intact HPM is vital for HIP1's survival role.
• HPM tyrosines are conserved and required for HIP1-related protein (HIP1r) phosphorylation.

Conclusions:

• RTK-mediated phosphorylation of HIP1 in its N-terminal region promotes cellular survival.
• The HPM and its phosphorylation status are critical for HIP1 function in cell survival.
• HIP1 phosphorylation by RTKs represents a potential therapeutic target in cancers where HIP1 is elevated.