HPK1, a hematopoietic protein kinase activating the SAPK/JNK pathway

EMBO J. 1996 Dec 16;15(24):7013-25.


In mammalian cells, a specific stress-activated protein kinase (SAPK/JNK) pathway is activated in response to inflammatory cytokines, injury from heat, chemotherapeutic drugs and UV or ionizing radiation. The mechanisms that link these stimuli to activation of the SAPK/JNK pathway in different tissues remain to be identified. We have developed and applied a PCR-based subtraction strategy to identify novel genes that are differentially expressed at specific developmental points in hematopoiesis. We show that one such gene, hematopoietic progenitor kinase 1 (hpk1), encodes a serine/threonine kinase sharing similarity with the kinase domain of Ste20. HPK1 specifically activates the SAPK/JNK pathway after transfection into COS1 cells, but does not stimulate the p38/RK or mitogen-activated ERK signaling pathways. Activation of SAPK requires a functional HPK1 kinase domain and HPK1 signals via the SH3-containing mixed lineage kinase MLK-3 and the known SAPK activator SEK1. HPK1 therefore provides an example of a cell type-specific input into the SAPK/JNK pathway. The developmental specificity of its expression suggests a potential role in hematopoietic lineage decisions and growth regulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Bone Marrow / enzymology*
  • COS Cells
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cell Line
  • Cloning, Molecular
  • DNA, Complementary
  • Enzyme Activation
  • Gene Expression Regulation, Enzymologic*
  • JNK Mitogen-Activated Protein Kinases
  • Mice
  • Mitogen-Activated Protein Kinases*
  • Molecular Sequence Data
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA, Messenger / genetics
  • Sequence Homology, Amino Acid


  • DNA, Complementary
  • RNA, Messenger
  • hematopoietic progenitor kinase 1
  • Protein-Serine-Threonine Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases