Internalization and recycling of receptor-bound gonadotropin-releasing hormone agonist in pituitary gonadotropes

Journal Article · Tue Dec 15 04:00:00 EST 1987 · J. Biol. Chem.; (United States)

OSTI ID:5520945

Schvartz, I; Hazum, E

The fate of cell surface gonadotropin-releasing hormone (GnRH) receptors on pituitary cells was studied utilizing lysosomotropic agents and monensin. Labeling of pituitary cells with a photoreactive GnRH derivative, (azidobenzoyl-D-Lys6)GnRH, revealed a specific band of Mr = 60,000. When photoaffinity-labeled cells were exposed to trypsin immediately after completion of the binding, the radioactivity incorporated into the Mr = 60,000 band decreased, with a concomitant appearance of a proteolytic fragment (Mr = 45,000). This fragment reflects cell surface receptors. Following GnRH binding, the hormone-receptor complexes underwent internalization, partial degradation, and recycling. The process of hormone-receptor complex degradation was substantially prevented by lysosomotropic agents, such as chloroquine and methylamine, or the proton ionophore, monensin. Chloroquine and monensin, however, did not affect receptor recycling, since the tryptic fragment of Mr = 45,000 was evident after treatment with these agents. This suggests that recycling of GnRH receptors in gonadotropes occurs whether or not the internal environment is acidic. Based on these findings, we propose a model describing the intracellular pathway of GnRH receptors.

• Research Organization: Weizmann Institute of Science, Rehovot, Israel
• OSTI ID: 5520945
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 262:35; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AZIDES
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
BIOLOGICAL PATHWAYS
BODY
CHEMISTRY
ENDOCRINE GLANDS
ENZYMES
GLANDS
GONADOTROPINS
HORMONES
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
MATHEMATICAL MODELS
MEMBRANE PROTEINS
MOLECULAR WEIGHT
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PEPTIDE HYDROLASES
PHOTOCHEMISTRY
PITUITARY GLAND
PITUITARY HORMONES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
RESPONSE MODIFYING FACTORS
SERINE PROTEINASES
TRACER TECHNIQUES
TRYPSIN