Functional expression of corticotropin-releasing hormone (CRH) receptor 1 in cultured rat microglia.
Corticotropin-releasing hormone (CRH), known as a key regulator of the hypothalamic-pituitary-adrenal axis response to stress, elicits its biological effects by binding to two membrane receptors (CRH-R1 and CRH-R2). The present studies examined the presence of functional expression of CRH receptors in cultured microglia of rat. CRH-R1 mRNA and protein were detected by reverse transcriptase polymerase chain reaction (RT-PCR), western blotting and receptor chemical cross-linking assay in cultured microglia. CRH-R2 mRNA was undetectable by RT-PCR. The radioligand binding analysis using [125I]Tyr-rat/human CRH revealed a high affinity binding site (Kd of 1.2 nm and Bmax of 84 fmol/mg of protein). Competition studies using CRH and related peptides indicated kinetic and pharmacological characteristics consistent with the CRH-R1 receptor subtype. Receptor chemical cross-linking assay demonstrated a single band of CRH receptor with a molecular weight of -77 kDa, which was inhibited in the presence of excess unlabeled rat/human CRH in a dose-dependent manner and inhibited by a CRH receptor antagonist astressin. Functional coupled cAMP production in cultured microglia was stimulated by exogenous addition of CRH and related peptides in a dose-dependent manner and blocked by astressin. Our findings suggest the functional expression of CRH-R1 receptor in rat microglia, indicating an important mechanism of interaction between immune and neuroendocrine systems in brain physiological and pathological conditions.
Wang
Wei
W
Department of Pediatrics, Kingston General Hospital, Ontario, Canada.
Ji
Ping
P
Riopelle
Richard J
RJ
Dow
Kimberly E
KE
D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D003432:Cross-Linking Reagents / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D007457:Iodine Radioisotopes; D017628:Microglia / Q000166:cytology / Q000502:physiology*; D018696:Neuroprotective Agents / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011869:Radioligand Assay; D051381:Rats; D018019:Receptors, Corticotropin-Releasing Hormone / Q000235:genetics* / Q000378:metabolism*
D003432:Cross-Linking Reagents; D007457:Iodine Radioisotopes; D018696:Neuroprotective Agents; D010446:Peptide Fragments; D012333:RNA, Messenger; D018019:Receptors, Corticotropin-Releasing Hormone; C104416:astressin; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP