An S116R Phosphorylation Site Mutation in Human Fibroblast Growth Factor-1 Differentially Affects Mitogenic and Glucose-Lowering Activities

Xue Xia, Ozan S. Kumru, Sachiko I. Blaber, C. Russell Middaugh, Ling Li, David M. Ornitz, Jae Myoung Suh, Annette R. Atkins, Michael Downes, Ronald M. Evans, Connie A. Tenorio, Ewa Bienkiewicz, Michael Blaber

Research output: Contribution to journalArticlepeer-review

Abstract

Fibroblast growth factor-1 (FGF-1), a potent human mitogen and insulin sensitizer, signals through both tyrosine kinase receptor–mediated autocrine/paracrine pathways as well as a nuclear intracrine pathway. Phosphorylation of FGF-1 at serine 116 (S116) has been proposed to regulate intracrine signaling. Position S116 is located within a ∼17 amino acid C-terminal loop that contains a rich set of functional determinants including heparin∖heparan sulfate affinity, thiol reactivity, nuclear localization, pharmacokinetics, functional half-life, nuclear ligand affinity, stability, and structural dynamics. Mutational targeting of specific functionality in this region without perturbing other functional determinants is a design challenge. S116R is a non-phosphorylatable variant present in bovine FGF-1 and other members of the human FGF family. We show that the S116R mutation in human FGF-1 is accommodated with no perturbation of biophysical or structural properties, and is therefore an attractive mutation with which to elucidate the functional role of phosphorylation. Characterization of S116R shows reduction in NIH 3T3 fibroblast mitogenic stimulation, increase in fibroblast growth factor receptor-1c activation, and prolonged duration of glucose lowering in ob/ob hyperglycemic mice. A novel FGF-1/fibroblast growth factor receptor-1c dimerization interaction combined with non-phosphorylatable intracrine signaling is hypothesized to be responsible for these observed functional effects.

Original languageEnglish
Pages (from-to)3507-3519
Number of pages13
JournalJournal of Pharmaceutical Sciences
Volume105
Issue number12
DOIs
StatePublished - Dec 1 2016

Keywords

  • X-ray crystallography
  • fibroblast growth factor receptor
  • heparan sulfate proteoglycan
  • human fibroblast growth factor-1
  • protein engineering
  • protein stability
  • thermodynamics

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