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Publication

The protein tyrosine kinase Hck is located on lysosomal vesicles that are physically and functionally distinct from CD63-positive lysosomes in human macrophages.

In macrophages, lysosomes are suspected to have a heterogenous population of vesicles. This study was thus undertaken to identify and to characterize lysosomal compartments in human macrophages. Hck is a Src-family tyrosine kinase associated with secretory lysosomes in neutrophils and with cytoplasmic vesicles in macrophages that fuse with phagosomes. We identified these Hck-positive vesicles and compared them to CD63-positive, M6PR-negative vesicles known as classical lysosomes. Hck vesicles exhibited lysosomal features. Indeed, Hck-positive vesicles could be loaded with rhodamine-dextran, which has been shown to accumulate in lysosomal compartments. Hck was delivered to zymosan-containing phagosomes at a late stage of the maturation process, which occurs after the fusion with CD63-positive lysosomes. Finally, when mycobacteria were used to prevent phagolysosome biogenesis, Hck was not recruited to phagosomes. Moreover, Hck lysosomes were physically and functionally distinct from CD63-lysosomes. For instance, sucrose induced swelling of CD63-lysosomes without affecting Hck-positive ones. Only CD63-lysosomes fused with phagosomes in a microtubule-dependent manner. Entry of particles through the mannose receptor and Fcgamma receptors drove the phagosome towards a fusion with CD63-lysosomes, whereas only Fcgamma receptors induced the mobilisation of Hck-lysosomes. This study provides further evidence for the existence of sub-populations of lysosomes in macrophages: one stained by CD63 and another one characterized by the presence of Hck. Therefore, Hck represents a new tool to study the fusion dynamics of lysosomal compartments and their subversion by several intracellular pathogens.

Publication date
January 1, 2002
Principal Investigators
Astarie-Dequeker C, Carréno S, Cougoule C, Maridonneau-Parini I
PubMed reference
J. Cell. Sci. 2002;115(Pt 1):81-9
PubMed ID
11801726
Affiliation
Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique UMR 5089, 205 Route de Narbonne, 31077 Toulouse, France. astarie@ipbs