The absorptive cell of the suckling rat ileum is specialized for the uptake and digestion of milk macromolecules from the intestinal lumen. The apical cytoplasm contains an extensive tubulocisternal system, a variety of vesicles and multivesicular bodies (MVB), and a giant phagolysosomal vacuole where digestion is completed. To determine if sorting of membrane-bound and fluid-phase macromolecules occurs in this elaborate endocytic system, we infused adsorptive and soluble tracers into ligated intestinal loops in vivo and examined their fates. Lysosomal compartments were identified by acid phosphatase histochemistry. Native ferritin and two ferritin-lectin conjugates that do not bind to ileal membranes (Con A, UEAI) served as soluble tracers. Horseradish peroxidase binds to ileal membranes and thus was not useful as a fluid-phase tracer in this system. Cationized ferritin and a lectin that binds to terminal B-D-galactosyl sites on ileal membranes (Ricinus communis agglutinin [RCAI]-ferritin) were used as tracer ligands. All tracers entered the wide apical invaginations of the luminal cell surface and were transported intracellularly. Membrane- bound tracers were found in coated pits and vesicles, and throughout the tubulocisternal system (where cationized ferritin is released from the membrane) and later, in large clear vesicles and MVB. In contrast, fluid-phase tracers appeared within 5 min in vesicles of various sizes and were not transported through the tubulocisternae, rather, they were concentrated in a separate population of vesicles of increasing size that contained amorphous dense material. Large clear vesicles, large dense vesicles, and MVB eventually fused with the giant supranuclear vacuole. Acid phosphatase activity was present in MVB and in the giant vacuole but was not present in most large vesicles or in the tubulocisternae. These results demonstrate that membrane-bound and soluble protein are transported to a common lysosomal destination via separate intracellular routes involving several distinct prelysosomal compartments.
Membrane-bound and fluid-phase macromolecules enter separate prelysosomal compartments in absorptive cells of suckling rat ileum
Published 1984 in Journal of Cell Biology
ABSTRACT
PUBLICATION RECORD
- Publication year
1984
- Venue
Journal of Cell Biology
- Publication date
1984-09-01
- Fields of study
Biology, Medicine
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- absorptive cell of suckling rat ileum
The epithelial cell type in the suckling rat ileum that mediates uptake of luminal milk macromolecules.
Aliases: ileal absorptive cell, suckling rat ileal absorptive cell
- acid phosphatase histochemistry
A staining approach used to identify lysosomal compartments by detecting acid phosphatase activity.
Aliases: acid phosphatase activity staining
- dense vesicles
A vesicle population characterized by amorphous dense internal material in the apical endocytic pathway.
Aliases: large dense vesicles, dense vesicular population
- fluid-phase tracers
Soluble endocytic cargo that does not bind ileal membranes and is used to follow fluid-phase uptake.
Aliases: soluble tracers
- giant supranuclear vacuole
The large apical vacuole in the absorptive cell that receives late endocytic cargo.
Aliases: giant phagolysosomal vacuole
- membrane-bound tracers
Ligand-bound endocytic cargo that associates with ileal membrane surfaces and is followed as membrane-bound material.
Aliases: adsorptive tracers, tracer ligands
- multivesicular bodies
Endocytic compartments containing multiple internal vesicles, abbreviated MVB in the abstract.
Aliases: MVB
- prelysosomal compartments
Intracellular endocytic compartments in the pathway leading toward lysosomes.
- tubulocisternal system
An extensive apical tubular and cisternal membrane network in the absorptive cell cytoplasm.
Aliases: tubulocisternae
REFERENCES
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