Enhancing integrin α1 inserted (I) domain affinity to ligand potentiates integrin α1β1-mediated down-regulation of collagen synthesis

Mingjian Shi, Vadim Pedchenko, Briana H. Greer, Wade D. Van Horn, Samuel A. Santoro, Charles R. Sanders, Billy G. Hudson, Brandt F. Eichman, Roy Zent, Ambra Pozzi

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Integrin α1β1 binding to collagen IV, which is mediated by the α1-inserted (I) domain, down-regulates collagen synthesis. When unligated, a salt bridge between Arg287 and Glu317 is thought to keep this domain in a low affinity conformation. Ligand binding opens the salt bridge leading to a high-affinity conformation. How modulating integrin α1β1 affinity alters collagen homeostasis is unknown. To address this question, we utilized a thermolysin-derived product of the α1α 2α1 network of collagen IV (α1α2α1(IV) truncated protomer) that selectively binds integrin α1β1. We show that an E317A substitution enhanced binding to the truncated protomer, consistent with a previous finding that this substitution eliminates the salt bridge. Surprisingly, we show that an R287A substitution did not alter binding, whereas R287E/E317R substitutions enhanced binding to the truncated protomer. NMR spectroscopy and molecular modeling suggested that eliminating the Glu 317 negative charge is sufficient to induce a conformational change toward the open state. Thus, the role played by Glu317 is largely independent of the salt bridge. We further show that cells expressing E317A or R287E/E317R substitutions have enhanced down-regulation of collagen IV synthesis, which is mediated by the ERK/MAPK pathway. In conclusion, we have demonstrated that modulating the affinity of the extracellular α1 I domain to collagen IV enhances outside-in signaling by potentiating ERK activation and enhancing the down-regulation of collagen synthesis.

Original languageEnglish (US)
Pages (from-to)35139-35152
Number of pages14
JournalJournal of Biological Chemistry
Issue number42
StatePublished - Oct 12 2012
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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