TY - JOUR
T1 - Annexin2 coating the surface of enlargeosomes is needed for their regulated exocytosis
AU - Lorusso, Anna
AU - Covino, Cesare
AU - Priori, Giuseppina
AU - Bachi, Angela
AU - Meldolesi, Jacopo
AU - Chieregatti, Evelina
PY - 2006/11/29
Y1 - 2006/11/29
N2 - 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.
AB - 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.
KW - Annexin2
KW - Cytoskeleton
KW - Enlargeosome
KW - Exocytosis
KW - Membrane traffic
UR - http://www.scopus.com/inward/record.url?scp=33751585018&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33751585018&partnerID=8YFLogxK
U2 - 10.1038/sj.emboj.7601419
DO - 10.1038/sj.emboj.7601419
M3 - Article
C2 - 17082761
AN - SCOPUS:33751585018
VL - 25
SP - 5443
EP - 5456
JO - EMBO Journal
JF - EMBO Journal
SN - 0261-4189
IS - 23
ER -