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Cationic defensins arise from charge‐neutralized propeptides: a mechanism for avoiding leukocyte autocytotoxicity?
Author(s) -
Michaelson David,
Rayner John,
Couto Marcelo,
Ganz Tomas
Publication year - 1992
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1002/jlb.51.6.634
Subject(s) - biology , mechanism (biology) , cationic polymerization , immunology , biophysics , physics , chemistry , organic chemistry , quantum mechanics
Defensins, small cationic polypeptides with antimicrobial and cytotoxic properties, are among the principal constituents of cytoplasmic granules of mammalian neutrophils and certain macrophages. To identify conserved structural features of defensin precursors that may be important for their targeting to cytoplasmic granules or for prevention of autocytotoxicity, we isolated and sequenced three neutrophil‐specific rabbit defensin cDNAs that code for preproprotein precursors to the mature defensins NP‐3a, NP‐4, and NP‐5. The preprodefensins NP‐3a, NP‐4, and NP‐5, like the previously characterized preprodefensins, lack consensus sequences for N‐linked glycosylation, suggesting that defensins are targeted to lysosome‐like granules by a mechanism not dependent on the mannose‐6‐phosphate receptor. Analysis of all seven known myeloid prodefensins revealed a structure wherein an anionic propiece neutralizes the cationicity of the mature peptide. Because defensins apparently require cationic epitopes for cell membrane permeabilization and cytotoxicity, charge neutralization of mature peptides by their anionic propieces may prevent autocytotoxicity during defensin synthesis and processing.