Regulation of organelle movement in melanophores by protein kinase A (PKA), protein kinase C (PKC), and protein phosphatase 2A (PP2A)

Amy R. Reilein, Irina S. Tint, Natalia I. Peunova, Grigori N. Enikolopov, Vladimir I. Gelfand*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

73 Scopus citations


We used melanophores, cells specialized for regulated organelle transport, to study signaling pathways involved in the regulation of transport. We transfected immortalized Xenopus melanophores with plasmids encoding epitope-tagged inhibitors of protein phosphatases and protein kinases or control plasmids encoding inactive analogues of these inhibitors. Expression of a recombinant inhibitor of protein kinase A (PKA) results in spontaneous pigment aggregation. α-Melanocyte-stimulating hormone (MSH), a stimulus which increases intracellular cAMP, cannot disperse pigment in these cells. However, melanosomes in these cells can be partially dispersed by PMA, an activator of protein kinase C (PKC). When a recombinant inhibitor of PKC is expressed in melanophores, PMA-induced pigment dispersion is inhibited, but not dispersion induced by MSH. We conclude that PKA and PKC activate two different pathways for melanosome dispersion. When melanophores express the small t antigen of SV-40 virus, a specific inhibitor of protein phosphatase 2A (PP2A), aggregation is completely prevented. Conversely, overexpression of PP2A inhibits pigment dispersion by MSH. Inhibitors of protein phosphatase 1 and protein phosphatase 2B (PP2B) do not affect pigment movement. Therefore, melanosome aggregation is mediated by PP2A.

Original languageEnglish (US)
Pages (from-to)803-813
Number of pages11
JournalJournal of Cell Biology
Issue number3
StatePublished - Aug 10 1998


  • Cytoplasmic dynein
  • Kinesin II
  • Microtubule motors
  • Microtubules
  • Protein phosphorylation

ASJC Scopus subject areas

  • Cell Biology


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