title: Melanocortin 2 receptor-associated protein (MRAP) and MRAP2 in human adrenocortical tissues: regulation of expression and association with ACTH responsiveness.
abstract: BACKGROUND
  ACTH stimulates adrenocortical steroid production through the melanocortin 2 receptor (MC2R). MC2R trafficking and signaling are dependent on the MC2R accessory protein (MRAP). The MRAP homolog MRAP2 also transports the MC2R to the cell surface but might prevent activation.
  
  
  OBJECTIVE
  The objective of the investigation was to study the regulatory pathways of MRAP and MRAP2 and their contributions to ACTH responsiveness in human adrenal tissues.
  
  
  METHODS
  MRAP, MRAP2, and MC2R expression levels were studied in 32 human adrenocortical samples. Regulation of these mRNAs was investigated in 43 primary adrenal cultures, stimulated with ACTH, forskolin, angiotensin II (AngII), phorbol-12-myristate-13-acetate (PMA), or dexamethasone. The induction of cortisol, cAMP, and ACTH-responsive genes after treatment with ACTH was related to MRAP, MRAP2, and MC2R expression levels.
  
  
  RESULTS
  MRAP and MRAP2 levels were lower in adrenocortical carcinomas (ACC) than in other adrenal tissues (P < 0.001). Patient ACTH and cortisol levels were associated with adrenal levels of MRAP and MC2R in adrenal hyperplasia samples (P < 0.05) but not in tumors. ACTH induced the expression of MRAP 11 ± 2.1-fold and MC2R 20 ± 3.8-fold in all adrenal tissue types (mean ± SEM, both P < 0.0001), whereas AngII augmented these mRNAs 4.0 ± 1.2-fold and 12.6 ± 3.2-fold (P < 0.0001) in all but the ACC. MRAP2 expression was suppressed by forskolin (-24 ± 15%, P = 0.013) and PMA (-22 ± 7%, P = 0.0007). MRAP, MRAP2, or MC2R levels were not associated with the induction of cortisol, cAMP, or gene expression by ACTH in vitro.
  
  
  CONCLUSIONS
  MRAP and MC2R expression is induced by ACTH and AngII, which would facilitate cell surface receptor availability. Physiological expression levels of MRAP, MRAP2, and MC2R were not limiting for ACTH sensitivity.
authors.affiliation: Department of Internal Medicine, Erasmus Medical Center, Room Ee-532, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. j.hofland@erasmusmc.nl
authors.forename: Johannes
authors.initials: J
authors.lastname: Hofland
authors.forename: Patric J
authors.initials: PJ
authors.lastname: Delhanty
authors.forename: Jacobie
authors.initials: J
authors.lastname: Steenbergen
authors.forename: Leo J
authors.initials: LJ
authors.lastname: Hofland
authors.forename: Peter M
authors.initials: PM
authors.lastname: van Koetsveld
authors.forename: Francien H
authors.initials: FH
authors.lastname: van Nederveen
authors.forename: Wouter W
authors.initials: WW
authors.lastname: de Herder
authors.forename: Richard A
authors.initials: RA
authors.lastname: Feelders
authors.forename: Frank H
authors.initials: FH
authors.lastname: de Jong
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000302:Adrenal Cortex / Q000187:drug effects / Q000378:metabolism*; D000306:Adrenal Cortex Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018268:Adrenocortical Carcinoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000324:Adrenocorticotropic Hormone / Q000378:metabolism / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C458099:MRAP protein, human; C551627:MRAP2 protein, human; D008565:Membrane Proteins; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone