The scaffolding
protein, hematopoietic PBX-interacting
protein (
HPIP/PBXIP1), regulates cell migration necessary for
cancer cell dissemination. However, the mechanism that governs this process remains unknown. We show here that
HPIP expression is associated with stages of
breast cancer where cell dissemination results in poor patient outcome. Our investigation finds a novel association of
HPIP with
focal adhesion kinase (FAK) regulating FA dynamics. Interestingly, this interaction that led to activation of FAK
protein was mediated by the C-terminal domain of
HPIP and not the typical
integrin-binding motif. Further,
short hairpin RNA-mediated knockdown of FAK expression significantly reduced
HPIP-induced cell migration indicating participation of FAK pathway. Live-cell time-lapse imaging and biochemical analysis further established the role of
HPIP in microtubule-induced FA disassembly. We also found that
HPIP-mediated MAPK activation led to phosphorylation and subsequent activation of calpain2, and the activated calpain2 in turn proteolyses FA
protein,
talin. Interestingly,
HPIP is also proteolysed by calpain2 in
breast cancer cells. The proteolysis of
HPIP and
talin by calpain2, and the activation of calapin2 by
HPIP-mediated MAPK phosphorylation, is a novel regulatory axis to modulate the cell migration signal. Together, we have determined
HPIP as a novel activator of FAK and a new substrate of calpain2. These molecular interactions between
HPIP and FAK, and
HPIP and calpain2 regulate cell adhesion and migration through modulation of FA dynamics.