Characterization of a ligand for receptor protein-tyrosine kinase HTK expressed in immature hematopoietic cells

Seiji Sakano, Ryo Serizawa, Tomohisa Inada, Atsushi Iwama, Akira Itoh, Chihiro Kato, Yukiko Shimizu, Fumiko Shinkai, Renshi Shimizu, Shuhei Kondo, Mitsuharu Ohno, Toshio Suda

Research output: Contribution to journalArticlepeer-review

86 Citations (Scopus)


HTK is a receptor tyrosine kinase that belongs to the Eph subfamily. An extensive screening using BIAcore system revealed that a colon cancer cell line, C-1, expressed the ligand for HTK. From the conditioned medium of C-1 cells, a soluble form of ligand was purified by receptor affinity chromatography, and the isolation of full-length cDNA revealed that this ligand is identical to the human HTK Ligand (HTKL) previously reported. HTK receptor tyrosine phosphorylation was induced by membrane-bound or clustered soluble HTKL but not by unclustered soluble HTKL, indicating that HTKL requires cell-to-cell interaction for receptor activation. Binding analysis demonstrated that HTKL binds to HTK with a much higher affinity (K(d): 1.23 nM) than the other transmembrane-type ligand for Eph family, LERK-2/ELKL (K(d): 135 nM). The expression of HTK in cord blood cells was upregulated after the culture in the presence of stem cell factor. Clustered soluble HTKL stimulated the proliferation of sorted HTK+ cord blood cells and a hematopoietic cell line, UT-7/EPO from which HTK was isolated. These findings suggest the involvement of HTK-HTKL system in the proliferation of HTK+ hematopoietic progenitor cells in the hematopoietic environment.

Original languageEnglish
Pages (from-to)813-822
Number of pages10
Issue number4
Publication statusPublished - 1996
Externally publishedYes


  • BIAcore
  • HTK
  • HTK ligand
  • Hematopoietic cells
  • Receptor tyrosine kinase

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research


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