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Calreticulin and calnexin in the endoplasmic reticulum are important for phagocytosis
Author(s) -
MüllerTaubenberger Annette,
Lupas Andrei N,
Li Hewang,
Ecke Mary,
Simmeth Evelyn,
Gerisch Günther
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.23.6772
Subject(s) - calreticulin , calnexin , endoplasmic reticulum , biology , phagosome , microbiology and biotechnology , phagocytosis , chaperone (clinical) , mutant , biochemistry , gene , medicine , pathology
Calreticulin and calnexin are Ca 2+ ‐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 Ca 2+ storage capacity of calreticulin and calnexin might directly modulate activities of the actin system during particle uptake.