Eph receptors discriminate specific ligand oligomers to determine alternative signaling complexes, attachment, and assembly responses (original) (raw)

  1. Elke Stein,
  2. Andrew A. Lane,
  3. Douglas Pat Cerretti,
  4. Harald O. Schoecklmann,
  5. Alfred D. Schroff,
  6. Robert L. Van Etten, and
  7. Thomas O. Daniel
  8. Departments of Cell Biology, Pharmacology, and Medicine and the Vanderbilt Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee 37232 USA; Immunex Corporation, Seattle, Washington 98101 USA; University of Erlangen-Nurnberg, D-91054 Erlangen, Germany, Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393 USA

Abstract

Eph family receptor tyrosine kinases (including EphA3, EphB4) direct pathfinding of neurons within migratory fields of cells expressing gradients of their membrane-bound ligands. Others (EphB1 and EphA2) direct vascular network assembly, affecting endothelial migration, capillary morphogenesis, and angiogenesis. To explore how ephrins could provide positional labels for cell targeting, we tested whether endogenous endothelial and P19 cell EphB1 (ELK) and EphB2 (Nuk) receptors discriminate between different oligomeric forms of an ephrin-B1/Fc fusion ligand. Receptor tyrosine phosphorylation was stimulated by both dimeric and clustered multimeric ephrin-B1, yet only ephrin-B1 multimers (tetramers) promoted endothelial capillary-like assembly, cell attachment, and the recruitment of low-molecular-weight phosphotyrosine phosphatase (LMW–PTP) to receptor complexes. Cell–cell contact among cells expressing both EphB1 and ephrin-B1 was required for EphB1 activation and recruitment of LMW–PTP to EphB1 complexes. The EphB1-binding site for LMW–PTP was mapped and shown to be required for tetrameric ephrin-B1 to recruit LMW–PTP and to promote attachment. Thus, distinct EphB1-signaling complexes are assembled and different cellular attachment responses are determined by a receptor switch mechanism responsive to distinct ephrin-B1 oligomers.

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