In vivo regulation of human CrkII by cyclophilin A and FK506-binding protein

Pulak Ranjan Nath, Guangyu Dong, Alex Braiman, Noah Isakov

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Members of the Crk family of adaptor proteins are key players in signal transduction from a variety of cell surface receptors. CrkI and CrkII are two alternative-spliced forms of a single gene which possess an N-terminal SH2 domain and an SH3 domain that mediate interaction with other proteins. CrkII possesses an additional C-terminal linker region plus an extra SH3 domain, which does not interact with other proteins, but operates as regulatory moiety. Utilizing human Jurkat T cells, we demonstrate that CrkII-SH3N binding of C3G is inhibited by cyclosporin A (CsA) plus FK506 that inhibit the cyclophilin A (CypA) and FK506 binding protein (FKBP) peptidyl-prolyl cis-trans isomerases (PPIases; also termed immunophilins), respectively. Jurkat T cells were found to express ∼5-fold lower levels of CrkI protein compared to CrkII, but the efficiency of C3G binding by CrkI was ∼5-fold higher than that of CrkII, suggesting that the majority of cellular CrkII proteins adopt a conformation that is inaccessible for C3G. Treatment of Jurkat T cells with CsA plus FK506 led to a time-dependent conformational change in overexpressed human CrkII1-236 protein-containing FRET-based biosensor, supporting the accumulation of cis conformers of human CrkII1-236 in the presence of PPIase inhibitors. Our data suggest that the Gly219-Pro-Tyr motif in the human CrkII linker region serves as the recognition and isomerization site of PPIases, and raise the possibility that CsA and FK506 might interfere with selected effector T cell functions via a CrkII-, but not CrkI-dependent mechanisms.

Original languageEnglish
Pages (from-to)411-416
Number of pages6
JournalBiochemical and Biophysical Research Communications
Issue number2
StatePublished - 5 Feb 2016


  • Crk adaptor protein
  • Cyclophilin A
  • Cyclosporine A
  • Immunophilins
  • PPIase
  • Peptidyl-prolyl cis-trans isomerase

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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