Homotypic secretory vesicle fusion induced by the protein tyrosine phosphatase MEG2 depends on polyphosphoinositides in T cells.
Sec14p homology domains are found in a large number of proteins from plants, yeast, invertebrates, and higher eukaryotes. We report that the N-terminal Sec14p homology domain of the human protein tyrosine phosphatase PTP-MEG2 binds phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P(3)) in vitro and colocalizes with this lipid on secretory vesicle membranes in intact cells. Point mutations that prevented PtdIns(3,4,5)P(3) binding abrogated the capacity of PTP-MEG2 to induce homotypic secretory vesicle fusion in cells. Inhibition of cellular PtdIns(3,4,5)P(3) synthesis also rapidly reversed the effect of PTP-MEG2 on secretory vesicles. Finally, we show that several different phosphoinositide kinases colocalize with PTP-MEG2, thus allowing for local synthesis of PtdIns(3,4,5)P(3) in secretory vesicle membranes. We suggest that PTP-MEG2 through its Sec14p homology domain couples inositide phosphorylation to tyrosine dephosphorylation and the regulation of intracellular traffic of the secretory pathway in T cells.
Huynh
Huong
H
Program of Signal Transduction, Cancer Research Center, The Burnham Institute, La Jolla, CA 92037, USA.
Wang
Xiaodong
X
Li
Weizhong
W
Bottini
Nunzio
N
Williams
Scott
S
Nika
Konstantina
K
Ishihara
Hisamitsu
H
Godzik
Adam
A
Mustelin
Tomas
T
D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D003198:Computer Simulation; D006801:Humans; D007424:Intracellular Fluid / Q000201:enzymology; D007425:Intracellular Membranes / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D019169:Jurkat Cells; D008561:Membrane Fusion / Q000235:genetics / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018129:Phosphatidylinositol Phosphates / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D049294:Phospholipid Transfer Proteins; D010766:Phosphorylation; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000502:physiology; D022142:Secretory Vesicles / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000201:enzymology / Q000378:metabolism*
D002352:Carrier Proteins; D008565:Membrane Proteins; D018129:Phosphatidylinositol Phosphates; D049294:Phospholipid Transfer Proteins; D011993:Recombinant Fusion Proteins; C060974:phosphatidylinositol 3,4,5-triphosphate; D019870:1-Phosphatidylinositol 4-Kinase; C447615:PTPN9 protein, human; D017027:Protein Tyrosine Phosphatases; D054558:Protein Tyrosine Phosphatases, Non-Receptor