Mechanistic basis for the activation of plant membrane receptor kinases by SERK-family coreceptors

Proc Natl Acad Sci U S A. 2018 Mar 27;115(13):3488-3493. doi: 10.1073/pnas.1714972115. Epub 2018 Mar 12.

Abstract

Plant-unique membrane receptor kinases with leucine-rich repeat ectodomains (LRR-RKs) can sense small molecule, peptide, and protein ligands. Many LRR-RKs require SERK-family coreceptor kinases for high-affinity ligand binding and receptor activation. How one coreceptor can contribute to the specific binding of distinct ligands and activation of different LRR-RKs is poorly understood. Here we quantitatively analyze the contribution of SERK3 to ligand binding and activation of the brassinosteroid receptor BRI1 and the peptide hormone receptor HAESA. We show that while the isolated receptors sense their respective ligands with drastically different binding affinities, the SERK3 ectodomain binds the ligand-associated receptors with very similar binding kinetics. We identify residues in the SERK3 N-terminal capping domain, which allow for selective steroid and peptide hormone recognition. In contrast, residues in the SERK3 LRR core form a second, constitutive receptor-coreceptor interface. Genetic analyses of protein chimera between BRI1 and SERK3 define that signaling-competent complexes are formed by receptor-coreceptor heteromerization in planta. A functional BRI1-HAESA chimera suggests that the receptor activation mechanism is conserved among different LRR-RKs, and that their signaling specificity is encoded in the kinase domain of the receptor. Our work pinpoints the relative contributions of receptor, ligand, and coreceptor to the formation and activation of SERK-dependent LRR-RK signaling complexes regulating plant growth and development.

Keywords: brassinosteroid signaling; floral abscission; leucine-rich repeat domain; membrane receptor kinase; receptor activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / growth & development
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / metabolism*
  • Kinetics
  • Ligands
  • Plant Development
  • Protein Binding
  • Protein Conformation
  • Protein Kinases / chemistry
  • Protein Kinases / metabolism*
  • Protein-Serine-Threonine Kinases / chemistry
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proteins / chemistry
  • Proteins / metabolism*
  • Receptors, Cell Surface / chemistry
  • Receptors, Cell Surface / metabolism*
  • Signal Transduction

Substances

  • Arabidopsis Proteins
  • Ligands
  • Proteins
  • Receptors, Cell Surface
  • leucine-rich repeat proteins
  • Protein Kinases
  • RLK5 protein, Arabidopsis
  • SERK1 protein, Arabidopsis
  • BRI1 protein, Arabidopsis
  • Protein-Serine-Threonine Kinases

Associated data

  • PDB/6FIF