Systems-level identification of PKA-dependent signaling in epithelial cells

Kiyoshi Isobe, Hyun Jun Jung, Chin Rang Yang, J’Neka Claxton, Pablo Sandoval, Maurice B. Burg, Viswanathan Raghuram, Mark A. Knepper

Research output: Contribution to journalArticlepeer-review

Abstract

G protein stimulatory α-subunit (Gαs)-coupled heptahelical receptors regulate cell processes largely through activation of protein kinase A (PKA). To identify signaling processes downstream of PKA, we deleted both PKA catalytic subunits using CRISPR-Cas9, followed by a “multiomic” analysis in mouse kidney epithelial cells expressing the Gαs-coupled V2 vasopressin receptor. RNA-seq (sequencing)–based transcriptomics and SILAC (stable isotope labeling of amino acids in cell culture)-based quantitative proteomics revealed a complete loss of expression of the water-channel gene Aqp2 in PKA knockout cells. SILAC-based quantitative phosphoproteomics identified 229 PKA phosphorylation sites. Most of these PKA targets are thus far unannotated in public databases. Surprisingly, 1,915 phosphorylation sites with the motif x-(S/T)-P showed increased phosphooccupancy, pointing to increased activity of one or more MAP kinases in PKA knockout cells. Indeed, phosphorylation changes associated with activation of ERK2 were seen in PKA knockout cells. The ERK2 site is downstream of a direct PKA site in the Rap1GAP, Sipa1l1, that indirectly inhibits Raf1. In addition, a direct PKA site that inhibits the MAP kinase kinase kinase Map3k5 (ASK1) is upstream of JNK1 activation. The datasets were integrated to identify a causal network describing PKA signaling that explains vasopressin-mediated regulation of membrane trafficking and gene transcription. The model predicts that, through PKA activation, vasopressin stimulates AQP2 exocytosis by inhibiting MAP kinase signaling. The model also predicts that, through PKA activation, vasopressin stimulates Aqp2 transcription through induction of nuclear translocation of the acetyltransferase EP300, which increases histone H3K27 acetylation of vasopressin-responsive genes (confirmed by ChIP-seq).

Original languageEnglish (US)
Pages (from-to)E8875-E8884
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number42
DOIs
StatePublished - Oct 17 2017
Externally publishedYes

Keywords

  • CRISPR-Cas9
  • Next-generation sequencing
  • Phosphoproteomics
  • Protein mass spectrometry
  • Vasopressin

ASJC Scopus subject areas

  • General

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