Follicle-stimulating hormone-regulated Sertoli cell proteins SCc1 and SCc2 are phosphorylated and mitochondrially associated.
Sertoli cell intracellular protein 1 (SCc1) and 2 (SCc2) are polypeptides found in rat Sertoli cell cultures incubated with either FSH or (Bu)2cAMP. They were first identified in [35S]methionine-labeled Sertoli cell lysates using two-dimensional gel electrophoresis. Here we extend these observations by showing that SCc1 and SCc2 are present in rat seminiferous tubules, ovaries, and granulosa cells incubated with either FSH or (Bu)2cAMP and in testicular peritubular cells incubated with (Bu)2cAMP. Peritubular cells do not, however, respond to FSH with the production of SCc1 and SCc2. Peptide mapping with N-chlorosuccinimide revealed that SCc1 and SCc2 have similar cleavage patterns, suggesting a common primary amino acid sequence that is modified posttranslationally. Metabolic labeling with [32P]orthophosphate provided direct evidence that SCc1 and SCc2 are phosphoproteins. A shift in mobility of SCc1 and SCc2 toward the basic region of the gel to positions designated SCc1' and SCc2' occurred when cell lysates were treated with alkaline phosphatase before electrophoresis, providing additional evidence that SCc1 and SCc2 are phosphoproteins. SCc1 and SCc2 are also shown to be mitochondrially-associated in the Sertoli cell. Peptide maps of SCc1, SCc2, SCc1', and SCc2' obtained by treatment with alpha-chymotrypsin, are identical to proteolytic maps of proteins pp30', p30, and pp30 from adrenocortical cells. SCc1, SCc2, SCc1', and SCc2' are homologous with regard to their regulated expression, electrophoretic mobility, and mitochondrial localization to the adrenal proteins pp30' and pp30 as well as a series of 30 kilodalton proteins from MA-10 Leydig tumor cells. Both the adrenal cell proteins and the Leydig tumor cell proteins are thought to participate in cholesterol transport to the inner mitochondrial membrane, providing substrate for the cholesterol side-chain cleavage enzyme complex, an activity which the Sertoli cell does not perform, suggesting that alternative functions must be sought for SCc1 and SCc2 in Sertoli cells.
Gregory
C W
CW
Department of Cell Biology, Neurobiology and Anatomy, Ohio State University College of Medicine, Columbus 43210.
DePhilip
R M
RM
D000302:Adrenal Cortex / Q000737:chemistry / Q000166:cytology; D000469:Alkaline Phosphatase / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002918:Chymotrypsin; D000242:Cyclic AMP / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D006107:Granulosa Cells / Q000737:chemistry / Q000166:cytology; D007984:Leydig Cell Tumor / Q000737:chemistry / Q000473:pathology; D008297:Male; D008928:Mitochondria / Q000737:chemistry*; D010449:Peptide Mapping; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D011506:Proteins / Q000032:analysis* / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012671:Seminiferous Tubules / Q000737:chemistry / Q000166:cytology; D017386:Sequence Homology, Amino Acid; D012708:Sertoli Cells / Q000737:chemistry / Q000166:cytology; D013347:Subcellular Fractions; D013388:Succinimides; D013462:Sulfur Radioisotopes; D013736:Testicular Neoplasms / Q000737:chemistry / Q000473:pathology; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000473:pathology
D010761:Phosphorus Radioisotopes; D011506:Proteins; D013388:Succinimides; D013462:Sulfur Radioisotopes; C015752:N-chlorosuccinimide; D005640:Follicle Stimulating Hormone; D000242:Cyclic AMP; D000469:Alkaline Phosphatase; D002918:Chymotrypsin