Degradation rate of acetylcholine receptors inserted into denervated vertebrate neuromuscular junctions

Journal Article · Wed Feb 01 04:00:00 EST 1989 · J. Cell Biol.; (United States)

DOI:https://doi.org/10.1083/jcb.108.2.647· OSTI ID:6326743

Shyng, S L; Salpeter, M M

Many studies exist on the effect of denervation on the degradation of acetylcholine receptors (AChRs) at the vertebrate neuromuscular junction (nmj). These studies have described the behavior of either the total population of junctional receptors at different times after denervation, or of the receptors present at the time of denervation. No experimental studies yet exist on the degradation rate of the receptors newly inserted into denervated junctions. In the previous studies, the original receptors of mouse sternomastoid muscles were found to retain the slow degradation (t 1/2) of approximately 8-10 d of innervated junctional receptors for up to 10 d after denervation before accelerating to a t 1/2 of approximately 3 d. The total junctional receptors, on the other hand, showed a progressive increase in degradation rate from a t 1/2 of 8-10 d to a t 1/2 of 1 d. To reconcile these earlier observations, the present study examines the degradation of new receptors inserted into the nmj after denervation. To avoid possible contamination of the data with postdenervation extrajunctional receptors, we used transmission electron microscope autoradiography to study only receptors located at the postjunctional fold of the nmj. We established that the new receptors inserted into denervated junctions have a t 1/2 of approximately 1 d, considerably faster than that of the original receptors and equivalent to that of postdenervation extrajunctional receptors. Both original and new receptors are interspersed at the top of the junctional folds. Thus, until all the original receptors are degraded, the postjunctional membrane contains two populations of AChRs that maintain a total steady-state site density but degrade at different rates.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 6326743
• Journal Information: J. Cell Biol.; (United States), Journal Name: J. Cell Biol.; (United States) Journal Issue: 2 Vol. 108:2; ISSN JCLBA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ACETYLCHOLINE
AMINES
AMMONIUM COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
AUTORADIOGRAPHY
BIOLOGICAL HALF-LIFE
DRUGS
ELECTRON MICROSCOPY
ESTERS
MAMMALS
MEMBRANE PROTEINS
METABOLISM
MICE
MICROSCOPY
MUSCLES
NERVES
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
PARASYMPATHOMIMETICS
PROTEINS
QUATERNARY COMPOUNDS
RECEPTORS
RODENTS
TRANSMISSION ELECTRON MICROSCOPY
VERTEBRATES