Discovery proteomics identification of factors contributing to gonadotropin β expression

Abstract

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH), critical for reproduction, are heterodimers of a common α subunit and unique β subunits, that are limiting components in the mature hormone synthesis. GnRH from the hypothalamus regulates synthesis of LH and FSH β-subunits. Previous studies identified signaling pathways and transcription factors that mediate GnRH induction of β-subunits. However, these studies do not fully explain gonadotrope responsiveness to GnRH or mechanisms of how a single hormone can regulate two β-subunits differentially. We postulated additional transcription factors, coactivators or corepressors, that are awaiting identification. To provide novel candidates, we used discovery proteomics of protein complexes that associate with gonadotropin β promoters regions that contain GnRH-responsive elements, and protein complexes that interact with transcription factors that are activated by GnRH to induce gonadotropin β genes. Data are available via ProteomeXchange with identifier PXD075636. Using computational tools, such as Intervene and Tidyproteomics, we compare and contrast proteins in complexes to identify coactivators or corepressors that may be unique or in common for both gonadotropin β subunit transcriptional upregulation or repression, novel transcription factors, and proteins that may regulate both gonadotropin β gene expression, proteins specific to each promoter, and proteins that are recruited via interaction with intermediate GnRH-induced transcription factors. Our studies can serve as a resource to interrogate potential candidates in cell cultures and in vivo for their roles in gonadotropin β expression. Understanding the mechanisms whereby GnRH regulates gonadotropin hormone levels will provide insight into the physiology and pathophysiology of the reproductive system.