A1 Refereed original research article in a scientific journal
LAMP proteins are required for fusion of lysosomes with phagosomes
Authors: Huynh KK, Eskelinen EL, Scott CC, Malevanets A, Saftig P, Grinstein S
Publisher: NATURE PUBLISHING GROUP
Publication year: 2007
Journal: EMBO Journal
Journal name in source: EMBO JOURNAL
Journal acronym: EMBO J
Volume: 26
Issue: 2
First page : 313
Last page: 324
Number of pages: 12
ISSN: 0261-4189
DOI: https://doi.org/10.1038/sj.emboj.7601511
Abstract
Lysosome-associated membrane proteins 1 and 2 (LAMP-1 and LAMP-2) are delivered to phagosomes during the maturation process. We used cells from LAMP-deficient mice to analyze the role of these proteins in phagosome maturation. Macrophages from LAMP-1- or LAMP-2-deficient mice displayed normal fusion of lysosomes with phagosomes. Because ablation of both the lamp-1 and lamp-2 genes yields an embryonic-lethal phenotype, we were unable to study macrophages from double knockouts. Instead, we reconstituted phagocytosis in murine embryonic fibroblasts (MEFs) by transfection of Fc gamma IIA receptors. Phagosomes formed by Fc gamma IIA-transfected MEFs obtained from LAMP-1- or LAMP-2-deficient mice acquired lysosomal markers. Remarkably, although Fc gamma IIA-transfected MEFs from double-deficient mice ingested particles normally, phagosomal maturation was arrested. LAMP-1 and LAMP-2 double-deficient phagosomes acquired Rab5 and accumulated phosphatidylinositol 3-phosphate, but failed to recruit Rab7 and did not fuse with lysosomes. We attribute the deficiency to impaired organellar motility along microtubules. Time-lapse cinematography revealed that late endosomes/lysosomes as well as phagosomes lacking LAMP-1 and LAMP-2 had reduced ability to move toward the microtubule-organizing center, likely precluding their interaction with each other.
Lysosome-associated membrane proteins 1 and 2 (LAMP-1 and LAMP-2) are delivered to phagosomes during the maturation process. We used cells from LAMP-deficient mice to analyze the role of these proteins in phagosome maturation. Macrophages from LAMP-1- or LAMP-2-deficient mice displayed normal fusion of lysosomes with phagosomes. Because ablation of both the lamp-1 and lamp-2 genes yields an embryonic-lethal phenotype, we were unable to study macrophages from double knockouts. Instead, we reconstituted phagocytosis in murine embryonic fibroblasts (MEFs) by transfection of Fc gamma IIA receptors. Phagosomes formed by Fc gamma IIA-transfected MEFs obtained from LAMP-1- or LAMP-2-deficient mice acquired lysosomal markers. Remarkably, although Fc gamma IIA-transfected MEFs from double-deficient mice ingested particles normally, phagosomal maturation was arrested. LAMP-1 and LAMP-2 double-deficient phagosomes acquired Rab5 and accumulated phosphatidylinositol 3-phosphate, but failed to recruit Rab7 and did not fuse with lysosomes. We attribute the deficiency to impaired organellar motility along microtubules. Time-lapse cinematography revealed that late endosomes/lysosomes as well as phagosomes lacking LAMP-1 and LAMP-2 had reduced ability to move toward the microtubule-organizing center, likely precluding their interaction with each other.
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