The microtubule-binding protein hook3 interacts with a cytoplasmic domain of scavenger receptor A

Hitomi Sano, Masaho Ishino, Helmut Krämer, Takeyuki Shimizu, Hiroaki Mitsuzawa, Chiaki Nishitani, Yoshio Kuroki

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The class A scavenger receptor (SR-A) is a multifunctional transmembrane glycoprotein that is implicated in atherogenesis, innate immunity, and cell adhesion. Despite extensive structure-function studies of the receptor, intracellular molecules that directly interact with SR-A and regulate the receptor trafficking have not been determined. In the current study, we have identified a microtubule-binding protein, Hook3, as a novel interacting partner of SR-A. The association between a rat Hook3 isoform and SR-A was suggested by yeast two-hybrid screening and mass spectrometry analysis of SR-A-cytoplasmic domain-bound proteins in rat alveolar macrophages. The binding of overexpressed and endogenous human Hook3 to SR-A was demonstrated by pull-down assay and co-immunoprecipitations. Furthermore, endogenous murine SR-A and HK3 co-sedimented from cell lysates isolated from Raw 264.7 murine macrophage cells. The interaction of Hook3 with SR-A was significantly stimulated after SR-A had recognized the extracellular ligand. Studies using truncations demonstrated that the positively charged C-terminal Val614-Ala717 region of human Hook3 was required for the interaction with the negatively charged residues, Glu12, Asp13, and Asp15 in the human SR-A cytoplasmic domain. By transfecting small interfering RNA targeting Hook3, total and surface expression, receptor-mediated ligand uptake and protein stability of SR-A were significantly promoted, whereas the protein synthesis and maturation were not altered. We propose for the first time that Hook3 may participate in the turnover of the endocytosed scavenger receptor.

Original languageEnglish (US)
Pages (from-to)7973-7981
Number of pages9
JournalJournal of Biological Chemistry
Issue number11
StatePublished - Mar 16 2007

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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