Photoaffinity labelling of melanoma cell MSH receptors.
UV-irradiation at 365 nm of cultured Cloudman S91 mouse melanoma cells in the presence of photoreactive alpha-MSH analogues induced longlasting receptor stimulation as revealed by the ensuring activation of tyrosinase. Receptor labelling was more efficient with 4-diazirinophenyl and 2-nitro-4-azidophenyl photolabels than with 4-azidophenyl, and was further increased when superpotent [Nle4,D-Phe7]-alpha-MSH was used as ligand. Incubation of B16 melanoma cell membranes with mono-iodinated [Nle4,D-Phe7,Trp-(Naps)9]-alpha-MSH followed by UV-irradiation at 310-550 nm labelled a single band on SDS-PAGE with a molecular mass approximately or equal to 45 kDa. The displacement curve obtained in a competitive photolabelling experiment paralleled that of the binding assay, demonstrating that the labelling was specific.
Department of Research, University Hospital, Basel, Switzerland.
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D000345:Affinity Labels / Q000378:metabolism*; D000818:Animals; D007700:Kinetics; D009074:Melanocyte-Stimulating Hormones / Q000031:analogs & derivatives / Q000378:metabolism*; D008546:Melanoma, Experimental / Q000378:metabolism*; D051379:Mice; D011979:Receptors, Pituitary Hormone / Q000378:metabolism*
D000345:Affinity Labels; D011979:Receptors, Pituitary Hormone; C029446:MSH receptor; D009074:Melanocyte-Stimulating Hormones