Direct Binding of the Proline-rich Region of Protein Tyrosine Phosphatase 1B to the Src Homology 3 Domain of p130Cas

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摘要：

Protein tyrosine phosphatase 1B (PTP1B) is an abundant intracellular enzyme that is thought to act as a negative regulator of certain signaling pathways. The C terminus of PTP1B contains two proline-rich regions which conform to the canonical class II Src homology 3 domain binding motif, Pro- X - X -Pro- X -Arg. In this study, we establish that PTP1B interacts with Crk, Grb2, and p130 Cas in vitro and with at least one of these, p130 Cas , in intact cells. The interaction of PTP1B and p130 Cas is independent of tyrosine phosphorylation but can be disrupted by replacing two critical proline residues in the proline-rich domain of PTP1B between amino acids 301 and 315. When wild-type PTP1B is expressed in 3Y1-v- crk cells, p130 Cas shows substantial dephosphorylation, whereas the PTP1B proline mutant does not have this effect. In 3Y1 and 3Y1 v- crk -transformed fibroblasts, almost all of the total PTP1B and about 40% of total p130 Cas co-sediment with membranes composed primarily of endoplasmic reticulum. These results suggest that the proline-rich domain between amino acids 301 and 315 in PTP1B binds Src homology 3-containing proteins and that p130 Cas may be a physiological target of this phosphatase in cells.

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Animals Subcellular Fractions Cell Line Proline Ubiquitin-Protein Ligases Proto-Oncogene Proteins src Homology Domains Kinetics Amino Acid Sequence Proto-Oncogene Proteins c-cbl