Increased endocytosis and formation of multivesicular bodies in phorbol-ester-stimulated human monoblastic U-937 cells

Journal Article · Sat Apr 01 04:00:00 EST 1989 · Experimental Cell Research; (United States)

DOI:https://doi.org/10.1016/0014-4827(89)90111-0· OSTI ID:5533859

Nilsson, M ^[1]; Nilsson, K; Forsbeck, K ^[2]

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1. Univ. of Gothenburg (Sweden)
2. Uppsala Univ. Hospital (Sweden)

The phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) is known to arrest mitotic activity and induce macrophage differentiation in the U-937 monoblastic cell line. The acute effect of TPA on ultrastructural morphology and endocytic activity of U-937 cells was studied. TPA induced within 15 minutes {alpha} marked enlargement of multivesicular bodies (MVBs), comprising both volume and number of inclusion vesicles (other organelles appeared unchanged). At this stage the MVBs frequently showed tubular cytoplasmic extensions. Inclusion vesicles accumulated in MVBs with prolonged incubation (60 minutes). Cellular uptake of {sup 125}I-HRP was increased five times the control values already after 5 minutes of TPA stimulation. The uptake increased further with prolonged incubation (60 minutes), but at a slower rate. Together these indicate a TPA-induced transfer by endocytosis of portions of the plasma membrane to the lysosomal system via MVBs. Consideration of MVBs as part of the receptor-mediated endocytic pathway suggests that this effect of TPA might involve down-regulation of cell-surface receptors. The possibility of MVBs as a proton-sequestrating compartment, responsible for the cytoplasmic alkalinization previously reported for TPA-stimulated U-937 monoblastic cells, is discussed.

• OSTI ID: 5533859
• Journal Information: Experimental Cell Research; (United States), Journal Name: Experimental Cell Research; (United States) Vol. 181:2; ISSN ECREA; ISSN 0014-4827
• Country of Publication: United States
• Language: English

Related Subjects

550301* -- Cytology-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
BETA DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
CARCINOGENS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ELECTRON MICROSCOPY
ESTERS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE 125
IODINE ISOTOPES
ISOTOPES
MICROSCOPY
MORPHOLOGICAL CHANGES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PHORBOL ESTERS
PROMOTERS
RADIOISOTOPES
TRANSMISSION ELECTRON MICROSCOPY
TUMOR CELLS
TUMOR PROMOTERS
ULTRASTRUCTURAL CHANGES
UPTAKE