[Structural characterization of the somatostatin receptors on rat cerebrocortical membranes].
We characterized structurally the receptors for somatostatin in rat cerebral cortex by affinity labeling with [125I-Tyr1] somatostatin. [125I-Tyr1] somatostatin was cross-linked to cerebrocortical membranes using photoreactive cross-linker: N-5-azido-2-nitrobenzoyloxy-succinimide. Analysis by autoradiography revealed a broad band centered at Mr = 72,000 in the presence or absence of dithiothreitol. Affinity labeling of and specific [125I-Tyr1] somatostatin binding to cerebrocortical membranes were decreased similarly by adding unlabeled somatostatin or nonhydrolyzable guanine nucleotide analogue, guanyl-5'-yl imidodiphosphate, in a dose dependent manner. The pretreatment of cerebrocortical membranes with islet activating protein resulted in a decrease in subsequent affinity labeling of the protein. The cross-linked protein could be solubilized with Zwittergent 3-12 and poorly with digitonin, triton X-100 and NP-40. When exposed to agarose-coupled lectins, the solubilized labeled protein was absorbed to wheat germ agglutinin, partially to ricin communis-II, and not to concanavalin A or lentil lectin. The Mr = 72,000 protein bound to wheat germ agglutinin-agarose was eluted with not only N,N',N"-triacetylchitotriose but also N-acetylglucosamine. These results suggest that somatostatin receptors on cerebrocortical membranes are a monomeric glycoprotein with a Mr = 70,000 containing no disulfide-linked binding subunit, which is coupled to islet activating protein-sensitive guanine nucleotide regulatory protein.
Nagao
M
M
Second Department of Internal Medicine, Kobe University School of Medicine.
Sakamoto
C
C
Matozaki
T
T
Nishizaki
H
H
Konda
Y
Y
Nakano
O
O
Baba
S
S
D000818:Animals; D001345:Autoradiography; D001386:Azides; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D003432:Cross-Linking Reagents; D019204:GTP-Binding Proteins / Q000378:metabolism; D008297:Male; D008970:Molecular Weight; D037342:Pertussis Toxin; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000737:chemistry* / Q000378:metabolism; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000378:metabolism; D013388:Succinimides; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D001386:Azides; D003432:Cross-Linking Reagents; D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; D013388:Succinimides; D010566:Virulence Factors, Bordetella; D013004:Somatostatin; C049915:N-hydroxysuccinimidyl-5-azido-2-nitrobenzoate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins