Phosphatase Activity, Trimerization, and the C-terminal Polybasic Region Are All Required for PRL1-mediated Cell Growth and Migration

Abstract

The phosphatase of regenerating liver (PRL) phosphatases are implicated in a number of tumorigenesis and metastasis processes. The PRLs are unique among protein-tyrosine phosphatases in that they have extremely low phosphatase activity, a high propensity for trimer formation, and a polybasic region that precedes the C-terminal prenylation motif. To investigate the functional significance of these distinctive biochemical and structural features, we established a cell-based system in which ectopic PRL1 expression increased cell proliferation and migration, whereas knockdown of endogenous PRL1 abrogated these cellular activities. We showed that the intrinsic PRL1 phosphatase activity is obligatory for its biological function. We provided evidence that trimerization may be a general property for all PRL enzymes, and that PRL1 trimer formation is essential for the PRL1-mediated cell growth and migration. This finding indicates a novel mechanism for phosphatase regulation. We further demonstrated that the conserved C-terminal polybasic region is important for specific phosphoinositide recognition by PRL1. Both the polybasic residues and the adjacent prenylation motif are required for proper PRL1 subcellular localization and full biological activity.

PRL-1 Protein Promotes ERK1/2 and RhoA Protein Activation through a Non-canonical Interaction with the Src Homology 3 Domain of p115 Rho GTPase-activating Protein

“…p115 RhoGAP Negatively Regulates Cell Migration and ERK1/2 and RhoA Activation-It is well documented that PRL-1 promotes cell migration through activation of the ERK1/2 and RhoA pathways (10,11,13,14). It has also been reported that p115 RhoGAP inhibits cell motility through its GAP and C-terminal SH3 domains (31).…”

“…Recent biochemical studies revealed that PRL-1 promotes cell proliferation and invasion by up-regulating both the ERK1/2 and RhoA pathways (10,11,13,14). ERK1 and ERK2 are serine/threonine kinases that are required for many fundamental processes, including cell proliferation, survival, and motility (15), whereas the Rho family GTPases are recognized mainly as key regulators of actin cytoskeletal dynamics and cell migration (16,17).…”

“…PRL-1 also promotes cell invasion and tumor metastasis. For example, CHO or HEK293 cells stably expressing PRL-1 display enhanced motility and invasiveness (3,10). CHO cells with elevated PRL-1 also preferentially form metastatic tumors in nude mice (3).…”

New Approaches to Difficult Drug Targets: The Phosphatase Story

“…PTP4A1 is trimeric in the crystalline state and in solution. 83 Previous studies suggest that trimer formation is essential for PTP4A1-mediated cell growth and migration. Moreover, the interface responsible for PTP4A1 homotrimerization is shared by the other PTP4A family members.…”

“…This stimulated a computer-based virtual search for small molecules capable of disrupting PTP4A trimerization. 53,83 Biochemical and structural analyses identified compound 43, which binds to the PTP4A1 trimer interface and blocks trimerization of PTP4A1, PTP4A2, and PTP4A3. 53 Compound 43 also specifically abrogated the PTP4A1-induced cell proliferation and migration through attenuation of both ERK1/2 and AKT activity.…”