Zn2+ depletion blocks endosome fusion.

摘要: Fusion among endosomes is an important step for transport and sorting of internalized macromolecules. Working in a cell-free system, we previously reported that endosome fusion requires cytosol ATP, sensitive to N-ethylmaleimide. regulated by monomeric heterotrimeric GTP-binding proteins. We now report can proceed at very low Ca2+ concentrations, i.e. < 30 nM. Moreover, not affected when intravesicular depleted preincubation vesicles with calcium ionophores (5 microM ionomycin or A23187) the presence chelators mM EGTA 60 EDTA). The results indicate extremely concentrations extravesicular Ca2+. However, BAPTA [1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid], relatively specific chelator, inhibits fusion. binds other metals besides present evidence inhibition due chelation but Zn2+ depletion. TPEN [N,N,N',N'-tetrakis-(2-pyridylmethyl) ethylenediamine], another metal-ion chelator affinity Ca2+, also inhibited TPEN- BAPTA-inhibited fusions were restored addition Zn2+. Zn(2+)-dependent presents same characteristics as control In intact cells, along endocytic pathway. depletion blocks fusion, suggesting this ion necessary function one more factors involved process.