Relationship between endosomes and lysosomes.
Biochem Soc Trans
; 29(Pt 4): 476-80, 2001 Aug.
Article
en En
| MEDLINE
| ID: mdl-11498012
ABSTRACT
Delivery of endocytosed macromolecules to lysosomes occurs by means of direct fusion of late endosomes with lysosomes. This has been formally demonstrated in a cell-free content mixing assay using late endosomes and lysosomes from rat liver. There is evidence from electron microscopy studies that the same process occurs in intact cells. The fusion process results in the formation of hybrid organelles from which lysosomes are re-formed. The discovery of the hybrid organelle has opened up three areas of investigation (i) the mechanism of direct fusion of late endosomes and lysosomes, (ii) the mechanism of re-formation of lysosomes from the hybrid organelle, and (iii) the function of the hybrid organelle. Fusion has analogies with homotypic vacuole fusion in yeast. It requires syntaxin 7 as part of the functional trans-SNARE [SNAP receptor, where SNAP is soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein] complex and the release of lumenal calcium to achieve membrane fusion. Re-formation of lysosomes from the hybrid organelle occurs by a maturation process involving condensation of lumenal content and probably removal of some membrane proteins by vesicular traffic. Lysosomes may thus be regarded as a type of secretory granule, storing acid hydrolases in between fusion events with late endosomes. The hybrid organelle is predicted to function as a 'cell stomach', acting as a major site of hydrolysis of endocytosed macromolecules.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Endosomas
/
Endocitosis
/
Lisosomas
Tipo de estudio:
Prognostic_studies
Límite:
Animals
Idioma:
En
Revista:
Biochem Soc Trans
Año:
2001
Tipo del documento:
Article
País de afiliación:
Reino Unido