Abstract

Activation of the steroidogenic machinery by peptide hormones involves a number of steps for transmitting signals from the plasma membrane to mitochondria in a spatially and temporally coordinated manner. Although key proteins mediating the hormonal signal have been identified, recent data suggest that the pathway might involve more complex protein-protein and protein-lipid interactions. Genomic and proteomic methods of analysis, namely the Affymetrix Murine Genome U74A v2 GeneChip and the BD PowerBlot Western Array, were used to identify human chorionic gonadotropin (hCG)-induced changes in mRNA and protein of MA-10 Leydig tumor cells that parallel the increase seen in progesterone synthesis. To analyze the massive amount of data that was generated, a comprehensive protein information matrix summarizing the features of each gene or protein, including its known properties, as well as annotations derived by homology-based functional inference, was developed. Of the genes examined by Affymetrix array, approximately 79 were differentially expressed and of gene products examined by PowerBlot, 9 were differentially expressed (above twofold). Changes in the expression of selected transcripts of interest were confirmed using real-time quantitative polymerase chain reaction and immunoblot analyses. Collectively, these results indicate that hormonal regulation of steroidogenesis is a complex phenomenon, involving proteins that participate in various known and novel pathways, which are implicated in transmitting signals from the plasma membrane to mitochondria and nucleus.