MC1R curation notes

Deep research (falcon/perplexity-lite) unavailable in this environment; notes from UniProt Q01726 and
cached publications.

• Class A GPCR, 7 TM, for alpha/beta/gamma-MSH and ACTH; Gs -> adenylate cyclase -> cAMP/PKA -> MITF ->
  eumelanin (UniProt FUNCTION, ECO:0000269 multiple PMIDs).
• Localization: plasma membrane PMID:31097585;
  RHC variants R151C (ER) and R160W (cis-Golgi) retained intracellularly PMID:19452503.
  Conclusion: PM, N-terminus and extracellular loops exposed at the cell surface; secretory-pathway pools in transit.
• Modulators: MRAP/MRAP2 reduce responsiveness (PMID:19329486); MGRN1 competes with Gs (PMID:19737927);
  OPN3 (Gi) dampens cAMP (PMID:31097585).
• UV/DNA repair: MC1R-cAMP induces NR4A, promoting CPD removal (PMID:18292087) - regulatory, not repair machinery.
• Feeding-behavior IEAs from rat are melanocortin-family over-propagations (MC4R/MC3R role).