EPHA1

EPHA1 is an ephrin-A-class receptor tyrosine kinase that controls cell morphology and motility, acting as a negative regulator of cell spreading and migration upon ligand engagement (PMID:19118217). Ligand-binding studies establish that EPHA1 preferentially binds ephrin-A1 while retaining class-promiscuous binding to other A-type ephrin ligands, and that its expression is enriched in differentiated epithelial tissues including skin, thymus, kidney, and adrenal cortex (PMID:11519828). Mechanistically, ephrin-A1 stimulation drives EPHA1 to associate, via its C-terminal SAM domain, with the ankyrin region of integrin-linked kinase (ILK); this interaction is independent of EPHA1 kinase activity but requires ligand stimulation (PMID:19118217). Kinase-active EPHA1 suppresses ILK activity, and a constitutively active ILK mutant (S343D) rescues EPHA1-mediated spreading defects and attenuates RhoA activation, placing EPHA1 at the head of an ILK→RhoA→ROCK signaling axis that inhibits cell spreading and migration (PMID:19118217). Beyond these findings, no further mechanistic detail has been characterized in the available corpus.

1. 2001 Medium

   Defining the ligand specificity and tissue distribution of EPHA1 established it as an ephrin-A-class receptor expressed in differentiated epithelia, framing where its signaling is likely relevant.

   Evidence Soluble and native receptor binding assays, in situ hybridization on tissue sections, and genomic/chromosomal analysis of murine EphA1

   PMID:11519828

   Open questions at the time

   • Binding promiscuity across the full ephrin-A panel quantified only for murine receptor
   • Functional consequence of receptor expression in each tissue not addressed
   • No downstream signaling characterized in this study
2. 2009 High

   Linking EPHA1 to ILK answered how the receptor controls cell shape and motility, showing it acts through a kinase-independent SAM-domain interaction that suppresses ILK and engages RhoA-ROCK.

   Evidence Co-immunoprecipitation with domain-deletion mapping, ILK activity and RhoA activation assays, and rescue with the kinase-active ILK S343D mutant in cell spreading/migration assays

   PMID:19118217

   Open questions at the time

   • How kinase-active EPHA1 reduces ILK activity at the molecular level is not resolved
   • The downstream RhoA-ROCK effectors mediating spreading inhibition are not delineated
   • Findings derive from a single lab and defined cell systems

• The phosphorylation substrates of EPHA1 and the physiological contexts in which the ILK-RhoA-ROCK axis operates in vivo remain undefined.
• No direct kinase substrates identified
• No structural model of the EPHA1 SAM–ILK ankyrin interaction
• Physiological/developmental role in epithelial tissues not established