Excessive progesterone (PRG) may increase breast cancer risk under hormone therapy during postmenopause or hormonal contraception. As a sex steroid hormone, PRG exerts its cellular responses through signaling cascades involving classic (genomic), non-classic (non-genomic), or both combined responses by binding to either classic nuclear PRG receptors or non-classic membrane PRG receptors.Currently, the intricate balance and switch mechanisms between these two signaling cascades remain elusive. Three genes, KRIT1 (CCM1), MGC4607 (CCM2), and PDCD10 (CCM3), have been demonstrated to form a CCM signaling complex (CSC). In this report, we discover that the CSC plays an essential role in coupling both classic and non-classic PRG signaling pathways by mediating crosstalk between them. The coupled signaling pathways were detailed through high throughput omics.
One Sentence Summary:We discover a novel signaling network among the CCM signaling complex (CSC), classic and non-classic progesterone receptors, and their ligands-progesterone/mifepristone, is dynamically modulated and fine-tuned with a series of feedback regulations; perturbation of this intricate balance, such as hormone therapy in the postmenopause or hormonal contraception regimen, or perturbed CSC signaling could result in increased risks in breast cancer or compromising tumor therapy.Excessive progesterone (PRG) may increase breast cancer risk under hormone therapy during postmenopause or hormonal contraception. As a sex steroid hormone, PRG exerts its cellular responses through signaling cascades involving classic (genomic), non-classic (non-genomic), or both combined responses by binding to either classic nuclear PRG receptors or non-classic membrane PRG receptors (1).It has been well-defined that PRG commonly binds to its nuclear receptor (PR) as transcriptional factors in classic genomic actions (2). PR has two major isoforms (PR1/2) which are alternative transcripts with quite different cellular functions (2). PRG can evoke both genomic and non-genomic actions of the classical PR1/2. In non-genomic responses, PRG binds PR1/2, leading to rapid changes in intracellular calcium/chloride levels in a rapid non-classical mechanism (3), which is defined as membrane-initiated (non-genomic) actions. Recently, two new groups of membrane-bound PRG receptors which are unrelated to PR1/2 have been identified: 1). 5 members of membrane progestin receptors (mPRs)/the Class II progestin and adipoQ receptor (PAQRs); 2). 4 members of the b5-like heme/steroid-binding protein family known as sigma2 receptor (S2R)/progesterone receptor membrane components (PGRMCs) (4, 5).It has been shown that mPRs are highly expressed in reproductive tissues and function by coupling to G proteins (6) to execute their rapid non-classical actions. Homozygous mutant fish of all mPR genes were generated with no phenotype, suggesting redundancy shared by mPR genes (7). Three CCM genes, KRIT1 (CCM1), MGC4607 (CCM2), and PDCD10 (CCM3), form the CCM signaling complex (CSC) that mediates multiple si...