Abstract
Protein tyrosine phosphatase (PTP)-MEG2 is an intracellular tyrosine phosphatase that contains a Sec14 homology domain. We have purified the full-length and truncated forms of the enzyme from recombinant adenovirus-infected human 293 cells. By using lipid-membrane overlay and liposome binding assays, we demonstrated that PTP-MEG2 specifically binds phosphatidylserine among over 20 lipid compounds tested. The binding is mediated by its N-terminal Sec14 domain. In intact cells, the Sec14 domain is responsible for localization of PTP-MEG2 to the perinuclear region, and uploading of PS into the cell membrane causes translocation of PTP-MEG2 to the plasma membrane. Phosphatidylserine is a relatively abundant cell membrane phospholipid non-symmetrically distributed in the outer layer and inner layer of cell membranes. It has recently been defined as an important ligand for clearance of apoptotic cells. By specifically binding phosphatidylserine, PTP-MEG2 may play an important role in regulating signaling processes associated with phagocytosis of apoptotic cells.
Highlights
Protein tyrosine phosphatases (PTPs)1 consist of a highly diverse family of enzyme with crucial roles in cell signaling [1,2,3]
We examined the interaction of PTP-MEG2 with various known lipid molecules and demonstrated that phosphatidylserine (PS) interacts with PTP-MEG2
It has been well accepted that phospholipids are components of cell membranes and act as important second messengers [24]
Summary
Vol 278, No 25, Issue of June 20, pp. 22609 –22614, 2003 Printed in U.S.A. Specific Interaction of Protein Tyrosine Phosphatase-MEG2 with Phosphatidylserine*. Protein tyrosine phosphatase (PTP)-MEG2 is an intracellular tyrosine phosphatase that contains a Sec homology domain. PTP-MEG2 may play an important role in regulating signaling processes associated with phagocytosis of apoptotic cells. Protein tyrosine phosphatases (PTPs) consist of a highly diverse family of enzyme with crucial roles in cell signaling [1,2,3]. Beyond the limit of the catalytic domains are various segments or domains that modulate the activity and/or intracellular localization of the enzymes Among these is the Sec domain found in PTP-MEG2 [4]. PS is a relatively abundant membrane lipid molecule It has been defined as an important ligand for clearance of apoptotic cells through the PS receptor (PSR) located on the surface of phagocytes (10 –12). By interacting with PS, PTP-MEG2 may have an important role in regulating cell-signaling pathways in this process
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