Lactogen and LH receptors. Rat P-450 17 alpha, structural analysis and hormonal regulation of mRNA levels in the Leydig cell.
A complete amino acid sequence for rat testis P-450 17 alpha was deduced from nucleotide analysis of a cDNA clone isolated from a rat Leydig cell library. This cDNA expressed in COS-1 cells both 17 alpha-hydroxylase and 17,20 lyase activities. Rat P-450 17 alpha exhibited significant similarity to the nucleotide and deduced amino acid sequences of the bovine and human P-450 17 alpha, particularly with the highly conserved regions and secondary structure. The rat P-450 17 alpha is anchored to the ER by two transmembrane regions: the N-terminal insertion peptide and the stop-transfer sequence. The C-terminal is associated with the ER by four hydrophobic clefts including the steroid-binding site. We have demonstrated a dual effect of hCG, causing early increases of Leydig cell P-450 17 alpha mRNA levels at low doses, while higher desensitizing doses caused marked subsequent reduction of mRNA levels. Our studies demonstrate that gonadotropin stimulation and desensitization of P-450 17 alpha dependent enzymes (17 alpha-hydroxylase/17,20 desmolase) in the adult rat testis and E2 induced desensitization in fetal Leydig cells are related to levels of P-450 17 alpha mRNA.
Dufau
M L
ML
Molecular Endocrinology Section, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Minegishi
T
T
Buczko
E
E
Kitamura
M
M
Delgado
C
C
Namiki
M
M
D000818:Animals; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D005260:Female; D006031:Glycosylation; D006801:Humans; D007985:Leydig Cells / Q000502:physiology*; D008297:Male; D010053:Ovary / Q000502:physiology*; D010766:Phosphorylation; D011974:Receptors, LH / Q000502:physiology*; D011981:Receptors, Prolactin / Q000502:physiology*; D013254:Steroid 17-alpha-Hydroxylase / Q000502:physiology*; D013250:Steroid Hydroxylases / Q000502:physiology*; D013329:Structure-Activity Relationship
D011974:Receptors, LH; D011981:Receptors, Prolactin; D004247:DNA; D013250:Steroid Hydroxylases; D013254:Steroid 17-alpha-Hydroxylase