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Rapid and transient palmitoylation of the tyrosine kinase Lck mediates Fas signaling

  1. Darren Boehning1
  1. Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, Houston, TX 77030

  1. Edited by Solomon H. Snyder, Johns Hopkins University School of Medicine, Baltimore, MD, and approved August 13, 2015 (received for review May 26, 2015)

Significance

Protein palmitoylation has been proposed to mediate the recruitment of signaling proteins into lipid rafts. However, a significant shortcoming of this hypothesis is that the proposed kinetics of protein palmitoylation/depalmitoylation heretofore have been too slow to mediate very rapid signaling events. Using a combination of a highly sensitive palmitoylation assay with pulsed metabolic labeling, we were able to detect a population of the Src kinase Lck undergoing extremely rapid palmitoylation and depalmitoylation subsequent to Fas receptor stimulation. The rapid rise and fall in Lck palmitoylation was highly synchronized with other signaling events occurring during the first minutes after activation of the Fas pathway, suggesting the existence of a previously undescribed signal transduction mechanism.

Abstract

Palmitoylation is the posttranslational modification of proteins with a 16-carbon fatty acid chain through a labile thioester bond. The reversibility of protein palmitoylation and its profound effect on protein function suggest that this modification could play an important role as an intracellular signaling mechanism. Evidence that palmitoylation of proteins occurs with the kinetics required for signal transduction is not clear, however. Here we show that engagement of the Fas receptor by its ligand leads to an extremely rapid and transient increase in palmitoylation levels of the tyrosine kinase Lck. Lck palmitoylation kinetics are consistent with the activation of downstream signaling proteins, such as Zap70 and PLC-γ1. Inhibiting Lck palmitoylation not only disrupts proximal Fas signaling events, but also renders cells resistant to Fas-mediated apoptosis. Knockdown of the palmitoyl acyl transferase DHHC21 eliminates activation of Lck and downstream signaling after Fas receptor stimulation. Our findings demonstrate highly dynamic Lck palmitoylation kinetics that are essential for signaling downstream of the Fas receptor.

Footnotes

  • ↵1To whom correspondence may be addressed. Email: Askar.M.Akimzhanov{at}uth.tmc.edu or Darren.F.Boehning{at}uth.tmc.edu.

  • Author contributions: A.M.A. and D.B. designed research; A.M.A. performed research; A.M.A. and D.B. analyzed data; and A.M.A. and D.B. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1509929112/-/DCSupplemental.

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