Caspase-3 Regulates Catalytic Activity and Scaffolding Functions of the Protein Tyrosine Phosphatase PEST, a Novel Modulator of the Apoptotic Response

Abstract

The protein tyrosine phosphatase PEST (PTP-PEST) is involved in the regulation of the actin cytoskeleton. Despite the emerging functions attributed to both PTPs and the actin cytoskeleton in apoptosis, the involvement of PTP-PEST in apoptotic cell death remains to be established. Using several cell-based assays, we showed that PTP-PEST participates in the regulation of apoptosis. As apoptosis progressed, a pool of PTP-PEST localized to the edge of retracting lamellipodia. Expression of PTP-PEST also sensitized cells to receptor-mediated apoptosis. Concertedly, specific degradation of PTP-PEST was observed during apoptosis. Pharmacological inhibitors, immunodepletion experiments, and in vitro cleavage assays identified caspase-3 as the primary regulator of PTP-PEST processing during apoptosis. Caspase-3 specifically cleaved PTP-PEST at the 549 DSPD motif and generated fragments, some of which displayed increased catalytic activity. Moreover, caspase-3 regulated PTP-PEST interactions with paxillin, leupaxin, Shc, and PSTPIP. PTP-PEST acted as a scaffolding molecule connecting PSTPIP to additional partners: paxillin, Shc, Csk, and activation of caspase-3 correlated with the modulation of the PTP-PEST adaptor function. In addition, cleavage of PTP-PEST facilitated cellular detachment during apoptosis. Together, our data demonstrate that PTP-PEST actively contributes to the cellular apoptotic response and reveal the importance of caspases as regulators of PTPs in apoptosis.

TCR-induced downregulation of protein tyrosine phosphatase PEST augments secondary T cell responses

“…2D and E. We conclude that the downregulation of PTP-PEST upon T cell activation is either translational or post-translational. Although a proteasome inhibitor MG132 did not have any effect on the low levels of PTP-PEST in activated T cells, Caspase inhibitors tended to rescue the expression partially in our preliminary experiment (data not shown) as reported recently (Halle et al, 2007).…”

F-actin-binding domain of c-Abl regulates localized phosphorylation of C3G: role of C3G in c-Abl-mediated cell death

“…PTP-PEST localizes to membrane ruffles and retracting lamellipodia in apoptotic cells, and cleavage of PTP-PEST contributes to cellular detachment during apoptosis (Halle et al, 2007). As PTP-PEST negatively regulates c-Abl activity (Cong et al, 2000), it is possible that its degradation results in Abl activation.…”

PTP-PEST controls EphA3 activation and ephrin-induced cytoskeletal remodelling

“…5A). In addition to the full-length protein of ∼100 kDa, smaller molecular mass bands were also detected with an anti-PTP-PEST antibody (AG10) recognising the N-terminus, suggesting the presence of the cleaved PTP-PEST forms previously identified (Halle et al, 2007). To investigate this further, we transfected cells with a PTP-PEST construct (Fig.…”