Annexin2 coating the surface of enlargeosomes is needed for their regulated exocytosis

Anna Lorusso, Cesare Covino, Giuseppina Priori, Angela Bachi, Jacopo Meldolesi, Evelina Chieregatti

Research output: Contribution to journalArticlepeer-review

Abstract

Enlargeosomes are small cytoplasmic vesicles that undergo rapid, Ca 2+-dependent exo/endocytosis. The role of the cytoskeleton in these processes was unknown. In PC12-27 cells, microtubule disassembly had little effect on enlargeosomes, whereas microfilament disassembly increased markedly both their resting and stimulated exocytosis, and inhibited their endocytosis. Even at rest enlargeosomes are coated at their cytosolic surface by an actin-associated protein, annexin2, bound by a dual, Ca2+-dependent and Ca2+-independent mechanism. In contrast, the other enlargeosome marker, desmoyokin/Ahnak, is transported across the organelle membrane, apparently by an ABC transporter, and binds to its lumenal face. Annexin2-GFP expression revealed that, upon stimulation, the slow and random enlargeosome movement increases markedly and becomes oriented toward the plasma membrane. After annexin2 downregulation enlargeosome exocytosis induced by both [Ca 2+]i rise and cytoskeleton disruption is inhibited, and the NGF-induced differentiation is blocked. Binding of annexin2 to the enlargeosome membrane, the most extensive ever reported (>50% annexin2 bound to ∼3% of total membrane area), seems therefore to participate in the regulation of their exocytosis.

Original languageEnglish
Pages (from-to)5443-5456
Number of pages14
JournalEMBO Journal
Volume25
Issue number23
DOIs
Publication statusPublished - Nov 29 2006

Keywords

  • Annexin2
  • Cytoskeleton
  • Enlargeosome
  • Exocytosis
  • Membrane traffic

ASJC Scopus subject areas

  • Genetics
  • Cell Biology

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