ROCK1 phosphorylates and activates zipper-interacting protein kinase

Laura Hagerty, Douglas H. Weitzel, Jenica Chambers, Christopher N. Fortner, Matthew H. Brush, David Loiselle, Hiroshi Hosoya, Timothy A.J. Haystead

Research output: Contribution to journalArticlepeer-review

73 Scopus citations


Zipper-interacting protein kinase (ZIPK) regulates Ca2+- independent phosphorylation of both smooth muscle (to regulate contraction) and non-muscle myosin (to regulate non-apoptotic cell death) through either phosphorylation and inhibition of myosin phosphatase, the myosin phosphatase inhibitor CPI17, or direct phosphorylation of myosin light chain. ZIPK is regulated by multisite phosphorylation. Phosphorylation at least three sites Thr-180, Thr-225, and Thr-265 has been shown to be essential for full activity, whereas phosphorylation at Thr-299 regulates its intracellular localization. Herein we utilized an unbiased proteomics screen of smooth muscle extracts with synthetic peptides derived from the sequence of the regulatory phosphorylation sites of the enzyme to identify the protein kinases that might regulate ZIPK activity in vivo. Discrete kinase activities toward Thr-265 and Thr-299 were defined and identified by mass spectrometry as Rho kinase 1 (ROCK1). In vitro, ROCK1 showed a high degree of substrate specificity toward native ZIPK, both stoichiometrically phosphorylating the enzyme at Thr-265 and Thr-299 as well as bringing about activation. In HeLa cells, coexpression of ZIPK with ROCK1 altered the ROCK-induced phenotype of focused stress fiber pattern to a Rho-like phenotype of parallel stress fiber pattern. This effect was also dependent upon phosphorylation at Thr-265. Our findings provide a new regulatory pathway in smooth muscle and non-muscle cells whereby ROCK1 phosphorylates and regulates ZIP kinase.

Original languageEnglish (US)
Pages (from-to)4884-4893
Number of pages10
JournalJournal of Biological Chemistry
Issue number7
StatePublished - Feb 16 2007
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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