Zn2+ depletion blocks endosome fusion

被引:32
作者
Aballay, A
Sarrouf, MN
Colombo, MI
Stahl, PD
Mayorga, LS
机构
[1] UNIV NACL CUYO,CONICET,FAC CIENCIAS MED,INST HISTOL & EMBRYOL,RA-5500 MENDOZA,ARGENTINA
[2] WASHINGTON UNIV,SCH MED,DEPT CELL BIOL & PHYSIOL,ST LOUIS,MO 63110
关键词
D O I
10.1042/bj3120919
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
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 and ATP, and is sensitive to N-ethylmaleimide. Fusion is regulated by monomeric and heterotrimeric GTP-binding proteins. We now report that fusion can proceed at very low Ca2+ concentrations, i.e. < 30 nM. Moreover, fusion is not affected when intravesicular Ca2+ is depleted by preincubation of vesicles with calcium ionophores (5 mu M ionomycin or A23187) in the presence of calcium chelators (5 mM EGTA or 60 mM EDTA). The results indicate that fusion can proceed at extremely low concentrations of intravesicular and extravesicular Ca2+ However, BAPTA [1,2-bis-(o-aminophenoxy)ethane-N,N,N',N tetra-acetic acid], a relatively specific Ca2+ chelator, inhibits fusion. BAPTA binds other metals besides Ca2+. We present evidence that BAPTA inhibition is due not to Ca2+ chelation but to Zn2+ depletion. TPEN [N,N,N',N'-tetrakis-(2-pyridylmethyl) ethylenediamine], another metal-ion chelator with low affinity for Ca2+, also inhibited fusion. TPEN- and BAPTA-inhibited fusions were restored by addition of Zn2+. Zn2+-dependent fusion presents the same characteristics as control fusion. In intact cells, TPEN inhibited transport along the endocytic pathway. The results indicate that Zn2+ depletion blocks endosome fusion, suggesting that this ion is necessary for the function of one or more factors involved in the fusion process.
引用
收藏
页码:919 / 923
页数:5
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