Calreticulin and calnexin in the endoplasmic reticulum are important for phagocytosis
Calreticulin and calnexin in the endoplasmic reticulum are important for phagocytosis
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DOI：
10.1093/emboj/20.23.6772
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发表时间：
2001-12-03
期刊：
影响因子：
11.4
通讯作者：
Gerisch, G
中科院分区：
文献类型：
--
作者：
Müller-Taubenberger, A;Lupas, AN;Gerisch, G
钙网蛋白和钙连接蛋白是内质网中具有伴侣活性的钙结合蛋白。这些蛋白质已被删除的基因置换在网柄藻，唯一的微生物已知的港口这两种蛋白质;家庭成员在网柄藻位于系统发育树的基础。在缺乏钙网蛋白和钙连接蛋白的双突变体中观察到吞噬率的急剧下降，而在单突变体中仅发生轻微变化。网骨藻细胞是专职吞噬细胞，能够通过一系列活动内化颗粒：颗粒粘附到细胞表面，肌动蛋白依赖性吞噬杯的生长，以及吞噬体与质膜的分离。在双无效突变体中，颗粒仍然粘附在细胞表面，但吞噬杯的生长受到损害。在野生型细胞中表达的绿色荧光蛋白标记的钙网蛋白和钙连接蛋白揭示了内质网与包裹颗粒的吞噬杯的直接联系，使得钙网蛋白和钙连接蛋白的Ca 2+储存能力可能直接调节颗粒摄取期间肌动蛋白系统的活动。
Calreticulin and calnexin are Ca2+-binding proteins with chaperone activity in the endoplasmic reticulum. These proteins have been eliminated by gene replacement in Dictyostelium, the only microorganism known to harbor both proteins; family members in Dictyostelium are located at the base of phylogenetic trees. A dramatic decline in the rate of phagocytosis was observed in double mutants lacking calreticulin and calnexin, whereas only mild changes occurred in single mutants. Dictyostelium cells are professional phagocytes, capable of internalizing particles by a sequence of activities: adhesion of the particle to the cell surface, actin-dependent outgrowth of a phagocytic cup, and separation of the phagosome from the plasma membrane. In the double-null mutants, particles still adhered to the cell surface, but the outgrowth of phagocytic cups was compromised. Green fluorescent protein-tagged calreticulin and calnexin, expressed in wild-type cells, revealed a direct link of the endoplasmic reticulum to the phagocytic cup enclosing a particle, such that the Ca2+ storage capacity of calreticulin and calnexin might directly modulate activities of the actin system during particle uptake.