RT Journal Article
SR Electronic
T1 Demonstration of in vivo synthesis of pro-opiomelanocortin-, beta- endorphin-, and alpha-melanotropin-like species in the adult rat brain
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 956
OP 965
DO 10.1523/JNEUROSCI.04-04-00956.1984
VO 4
IS 4
A1 AS Liotta
A1 JP Advis
A1 JE Krause
A1 JF McKelvy
A1 DT Krieger
YR 1984
UL http://www.jneurosci.org/content/4/4/956.abstract
AB An in vivo labeling technique was utilized to demonstrate the in situ biosynthesis of pro-opiomelanocortin (POMC)-, beta-endorphin- and alpha- melanotropin (MSH)-like molecular species in rat brain. Unrestrained adult female rats were bilaterally cannulated in the hypothalamic arcuate nuclear region; [35S]methionine was infused either over a 15- min period with sacrifice 2 hr subsequently, or at a constant rate for 6 hr prior to sacrifice. Sequential immune-affinity chromatography and several chromatographic and electrophoretic techniques were employed to detect and characterize POMC-related material in the hypothalamic arcuate nuclear region, preoptic area, and median eminence. Four molecular species containing both corticotropin (ACTH) and beta- endorphin antigenic determinants within the same molecules were detected in the arcuate nuclear region and preoptic area. Two forms were similar to rat pituitary POMC with respect to apparent molecular weight (35,000 and 31,500) and [35S]methionine-containing tryptic fragments (one methionine each in N-terminal glycopeptide, ACTH, and beta-endorphin sequences of rat POMC). The other two forms (apparent Mr of 21,000 and 19,000) contained only the labeled tryptic fragments characteristic of ACTH and beta-endorphin. The detection of the latter forms suggests that POMC in brain, unlike its post-translational processing in rat pituitary, undergoes primary cleavage between the N- terminal peptide and the ACTH sequence. Peptides physicochemically indistinguishable from authentic beta-endorphin and des-acetyl alpha- MSH were detected in approximately equimolar amounts in all three brain regions. The ratio of POMC-like material to the alpha-MSH- and beta- endorphin-sized peptides was highest in the arcuate nuclear region, suggesting that POMC-like proteins are synthesized in the arcuate nuclear region and are processed into the smaller molecular species during axonal transport.