LH RECEPTOR - A NOVEL FAMILY OF G-PROTEIN COUPLED RECEPTORS

Monoclonal antibodies have been raised against porcine LH receptor and allowed to clone the corresponding messenger RNA from testicular cell s. The structure of the LH receptor have been determined. It shows sim ilarities but also differences to other G protein coupled receptors. I n particular a large extracellular domain is specific for that family of receptors. Variants forms of the LH receptor generated by alternati ve splicing and lacking transmembrane domains have been isolated. Immu nochemical and immunocytochemical studies have been performed. Three d ifferent forms of the LH receptor are physiologically expressed: a mat ure 85 kDa transmembrane species, a 68 kDa high mannose containing spe cies corresponding to a precursor which accumulate inside the cells, a nd truncated 45-48 kDa molecular weight species corresponding to the v ariant messenger RNAs identified during the cloning of the receptor. A novel zonation of the ovary has been described by immunocytochemical studies. Cross hybridisation with the LH receptor clone allowed to iso late the related human TSH receptor from thyroids. The human LH and FS H receptor genes have been localized to chromosome 2p21 and the TSH re ceptor gene to chromosome 14q31. The genes are very large and have int rons only within their 5' part corresponding to the extracellular doma in of the receptor.