Obliteration of alpha-melanocyte-stimulating hormone derived from POMC in pituitary and brains of PC2-deficient mice.
Alpha-melanocyte-stimulating hormone (alpha-MSH) is a neuropeptide expressed in pituitary and brain that is known to regulate energy balance, appetite control, and neuroimmune functions. The biosynthesis of alpha-MSH requires proteolytic processing of the proopiomelanocortin (POMC) precursor. Therefore, this study investigated the in vivo role of the prohormone convertase 2 (PC2) processing enzyme for production of alpha-MSH in PC2-deficient mice. Specific detection of alpha-MSH utilized radioimmunoassay (RIA) that does not crossreact with the POMC precursor, and which does not crossreact with other adrenocorticotropin hormone (ACTH) and beta-endorphin peptide products derived from POMC. alpha-MSH in PC2-deficient mice was essentially obliterated in pituitary, hypothalamus, cortex, and other brain regions (collectively), compared to wild-type controls. These results demonstrate the critical requirement of PC2 for the production of alpha-MSH. The absence of alpha-MSH was accompanied by accumulation of ACTH, ACTH-containing imtermediates, and POMC precursor. ACTH was increased in pituitary and hypothalamus of PC2-deficient mice, evaluated by RIA and reversed-phase high pressure liquid chromatography (RP-HPLC). Accumulation of ACTH demonstrates its role as a PC2 substrate that can be converted for alpha-MSH production. Further analyses of POMC-derived intermediates in pituitary, conducted by denaturing western blot conditions, showed accumulation of ACTH-containing intermediates in pituitaries of PC2-deficient mice, which implicate participation of such intermediates as PC2 substrates. Moreover, accumulation of POMC was observed in PC2-deficient mice by western blots with anti-ACTH and anti-beta-endorphin. In addition, increased beta-endorphin1-31 was observed in pituitary and hypothalamus of PC2-deficient mice, suggesting beta-endorphin1-31 as a substrate for PC2 in these tissues. Overall, these studies demonstrated that the PC2 processing enzyme is critical for the in vivo production of alpha-MSH in pituitary and brain.
Miller
Ruthellen
R
Buck Institute for Age Research, Novato, California 94945, USA.
Aaron
Wade
W
Toneff
Thomas
T
Vishnuvardhan
Daesety
D
Beinfeld
Margery C
MC
Hook
Vivian Y H
VY
D000324:Adrenocorticotropic Hormone / Q000032:analysis / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D002540:Cerebral Cortex / Q000737:chemistry / Q000378:metabolism; D007031:Hypothalamus / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010446:Peptide Fragments / Q000032:analysis / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000032:analysis / Q000378:metabolism*; D045706:Proprotein Convertase 2; D011863:Radioimmunoassay; D013381:Subtilisins / Q000172:deficiency* / Q000235:genetics; D000521:alpha-MSH / Q000032:analysis / Q000172:deficiency*; D001615:beta-Endorphin / Q000032:analysis / Q000378:metabolism
D010446:Peptide Fragments; D000521:alpha-MSH; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone; D013381:Subtilisins; D045706:Proprotein Convertase 2