A Golgi PKD activity reporter reveals a crucial role of PKD in nocodazole-induced Golgi dispersal

Traffic. 2009 Jul;10(7):858-67. doi: 10.1111/j.1600-0854.2009.00918.x. Epub 2009 Apr 25.

Abstract

The protein kinase D (PKD) family comprises multifunctional serine/threonine-specific protein kinases with three mammalian isoforms: PKD1, PKD2 and PKD3. A prominent PKD function is the regulation of basolateral-targeted transport carrier fission from the trans-Golgi network (TGN). To visualize site-specific PKD activation at this organelle, we designed a molecular reporter consisting of a PKD-specific substrate sequence fused to enhanced green fluorescent protein (EGFP), specifically targeted to the TGN via the p230 GRIP domain. Quantitative analyses using a phosphospecific antibody and ratiometric fluorescence imaging revealed that Golgi-specific phosphorylation of the reporter was strictly dependent on stimulation of endogenous PKD or transient expression of active PKD constructs. Conversely, PKD-specific pharmacological inhibitors and siRNA-mediated PKD knockdown suppressed reporter phosphorylation. Using this reporter we investigated a potential role for PKD in the regulation of Golgi complex morphology. Interestingly, nocodazole-induced Golgi complex break-up and dispersal was associated with local PKD activation as measured by reporter phosphorylation and this was efficiently blocked by expression of a dominant-negative PKD mutant or PKD depletion. Our data thus identify a novel link between PKD activity and the microtubule cytoskeleton, whereby Golgi complex integrity is regulated.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Enzyme Activation
  • Genes, Reporter*
  • Golgi Apparatus* / drug effects
  • Golgi Apparatus* / metabolism
  • Humans
  • Isoenzymes / metabolism*
  • Molecular Sequence Data
  • Nocodazole / pharmacology*
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / genetics
  • Protein Kinase C / metabolism*
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Tubulin Modulators / pharmacology*

Substances

  • Isoenzymes
  • RNA, Small Interfering
  • Recombinant Fusion Proteins
  • Tubulin Modulators
  • protein kinase D
  • Protein Kinase C
  • Nocodazole