Cloning of novel human SEC14p-like proteins: Ligand binding and functional properties

Petra Kempná, Jean Marc Zingg, Roberta Ricciarelli, Markus Hierl, Smita Saxena, Angelo Azzi

Research output: Contribution to journalArticlepeer-review

77 Scopus citations

Abstract

We describe the cloning and expression of two novel genes highly similar to the tocopherol-associated protein (hTAP/SEC14L2/SPF). Immunoprecipitation of the three recombinant hTAPs and extraction of their associated lipid-soluble molecules indicates that they bind not just tocopherols, but also phosphatidylinositol, phosphatidylcholine, and phosphatidylglycerol. Ligand competition analysis by isoelectric point mobility shift assay indicates that phosphatidylcholine, tocopherols, and tocopheryl-succinate compete with phosphatidylinositol binding to hTAPs. To investigate a possible function of hTAPs on enzymes involved in phospholipids metabolism, the activity of recombinant phosphatidylinositol 3-kinase (PI3Kγ/p110γ) was tested. Recombinant hTAPs reduce in vitro the activity of the recombinant catalytic subunit of PI3Kγ and stimulate it in the presence of α-tocopherol up to 5-fold. Immunoprecipitation of hTAP1 from cells results in co-precipitation of PI3-kinase activity, indicating a physical contact between the two proteins at a cellular level. In summary, hTAPs may modulate, in a tocopherol-sensitive manner, phosphatidylinositol-3-kinase, a central enzyme in signal transduction, cell proliferation, and apoptosis. It is possible that other phosphatidylinositol- and phosphatidylcholine-dependent signaling pathways are modulated by hTAPs and tocopherols, possibly by transporting and presenting these ligands to the corresponding enzymes.

Original languageEnglish (US)
Pages (from-to)1458-1472
Number of pages15
JournalFree Radical Biology and Medicine
Volume34
Issue number11
DOIs
StatePublished - Jun 1 2003
Externally publishedYes

Keywords

  • Free radicals
  • GOLD domain
  • Phospholipids
  • PI3-kinase
  • SEC14p
  • Tocopherol

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)

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