Regulatory role of kinases and phosphatases on the internalisation of caveolae in HepG2 cells

Erzsébet Botos, Ágnes Turi, Nándor Müllner, Ilona Kovalszky, Péter Tátrai, Anna L. Kiss

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The caveolar cycle is thought to be regulated by synchronised function of kinases and phosphatases. Using ocadaic acid - a serine/threonine protein phosphatase inhibitor - and an inhibitor of tyrosine phosphatase (sodium orthovanadate) we have followed the internalisation of caveolae. Since albumin binding to its receptor (gp60) can induce pinching off of caveolae from the plasma membrane, we also used this physiological ligand to induce the internalisation. Our confocal microscopic results show that both ocadaic acid and vanadate treatments have significantly decreased caveolin (caveolin-1 and -2) labelling on the cell surface, while the cytoplasmic labelling became much stronger. Quite often large, strongly labelled "granules" appear at the perinuclear region. Very strong caveolin labelling was detected along the actin-cytoskeleton suggesting that caveolae might move along these filaments. Our electron microscopic results also show an intensive caveolae pinching off from the plasma membrane. After ocadaic acid and vanadate treatments the number of surface connected vesicles (caveolae) decreases. At the same time, large multivesicular bodies (termed caveosomes) appear in the perinuclear area of the cytoplasm. By immunoprecipitation and Western blot analysis we detect an increased tyrosine phosphorylation of a ∼29 kDa protein in ocadaic acid and vanadate treated samples. This protein was identified as caveolin-2. No significant change in the tyrosine phosphorylation of caveolin-1 was found. From these data we can conclude that caveolae internalisation is regulated by phosphorylation of caveolin-2.

Original languageEnglish
Pages (from-to)313-320
Number of pages8
JournalMicron
Volume38
Issue number3
DOIs
Publication statusPublished - Apr 1 2007

Keywords

  • Caveolae
  • Caveolin-1
  • Caveolin-2
  • Protein phosphatases
  • Tyrosine phosphorylation

ASJC Scopus subject areas

  • Structural Biology
  • Materials Science(all)
  • Physics and Astronomy(all)
  • Cell Biology

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