Corticotropin releasing factor receptor type 1: molecular cloning and investigation of alternative splicing in the hamster skin.

The coding region of the hamster corticotropin releasing factor receptor type 1 was sequenced. Hamster gene appeared to be similar to mouse, rat, and human sequences with 95%, 94%, and 91% homology, respectively. Protein substitutions were generally found in the corticotropin releasing factor-binding domain. Thus, this domain can be more prone to mutations leading to changes in amino acid sequence. Hamster pituitary, eye, spleen, heart, skin, and four melanoma lines differentially expressed nine corticotropin releasing factor-R1 isoforms. These included the corticotropin releasing factor-R1alpha and corticotropin releasing factor-R1d homologs of human isoforms as well as e, f, h, j, k, m, and n isoforms. Corticotropin releasing factor-R1e mRNA had deletion of exons 3 and 4, CRF-R1j of exon 5, CRF-R1f of exon 11, CRF-R1k of exon 10, CRF-R1m of exons 11 and 12, and CRF-R1n of exons 10, 11, and 12. Corticotropin releasing factor-R1h had an insertion of a cryptic exon between exons 4 and 5. Reading frames of isoforms e, f, j, k, m, and h contained frameshifts, expected to produce truncated proteins. Corticotropin releasing factor-R1n isoform preserved the reading frame, but the transmembrane domains 6, 7, and one-third of the fifth were deleted. The AbC1 hamster melanoma cell line changed the pattern of alternative splicing after irradiation with ultraviolet light or induction of melanogenesis; this suggests that corticotropin releasing factor receptor alternative splicing may be regulated by common stressors, through modifications of activity and/or availability of splicing factors.