Dissection of membrane protein degradation mechanisms by reversible inhibitors

Journal Article · Sat Jun 25 04:00:00 EDT 1988 · J. Biol. Chem.; (United States)

OSTI ID:6924764

Hare, J F

The degradation of slowly turning over 125I-lactoperoxidase-labeled plasma membrane polypeptides in response to reversible temperature and lysosomotropic inhibitors was studied in rat hepatoma cultures. Cells were radiolabeled and left for 24 h to allow the removal of rapidly degraded proteins. Remaining trichloroacetic acid-precipitable protein was degraded (t 1/2 = 40-68 h) by an apparent first order process 60-86% sensitive to 10 mM NH4Cl or 5 mM methylamine and greater than 95% inhibited by temperature reduction to 18 degrees C. Thus, membrane proteins are selected for degradation in a time-dependent manner by a system which is sensitive to both 18 degrees C and to lysosomotropic amines. When inhibitory conditions were removed after 40-48 h, degradation of 125I-labeled protein resumed at the same rate as that seen in their absence. Since membrane proteins do not exhibit accelerated degradation after removal of inhibitory conditions, there can be no marking or sorting of those proteins destined for degradation during the 40-h exposure to inhibitory conditions. Exposure to amines or 18 degrees C did not affect the position of two-dimensionally resolved labeled polypeptides. Fractionation of labeled cells on Percoll gradients after 40 h of exposure to low temperature or amines showed that labeled protein remained in the plasma membrane fractions of the gradient although shifted to a slightly lower buoyant density in the presence of amines. These results support the notion that selection of plasma membrane proteins for degradation requires their internalization into acidic vesicles. Lysosomotropic amines and reduced temperature interfere with the selection process by preventing membrane fusion events.

• Research Organization: Oregon Health Sciences Univ., Portland (USA)
• OSTI ID: 6924764
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 263:18; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINES
ANIMALS
BETA DECAY RADIOISOTOPES
BIOLOGICAL FUNCTIONS
CELL CONSTITUENTS
CELL CULTURES
CELL MEMBRANES
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DISEASES
ELECTRON CAPTURE RADIOISOTOPES
FUNCTIONS
HEPATOMAS
INHIBITION
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NEOPLASMS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PROTEINS
RADIOISOTOPES
RATS
RODENTS
THERMODYNAMICS
TIME DEPENDENCE
TRACER TECHNIQUES
VERTEBRATES