Calcium-sensing receptor signaling in the regulation of colonic epithelial cells

钙敏感受体信号传导在结肠上皮细胞的调节中

• 批准号: 8970680
• 负责人: JUAN ENRIQUE ROZENGURT
• 金额: --
• 依托单位: VA GREATER LOS ANGELES HEALTHCARE SYSTEM
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8970680
• 关键词: Ablation; Adult; Amino Acids; Architecture; Aromatic Amino Acids; Calcium-Sensing Receptors; Cell Nucleus; Cell Proliferation; Cell membrane; Cell physiology; Cells; Cessation of life; Chemoprevention; Chief Cell; Colon; Colorectal Cancer; Diet; Down-Regulation; Employee Strikes; Epithelial Cell Proliferation; Epithelial Cells; Family; G-Protein-Coupled Receptors; GTP Binding; Gastrointestinal tract structure; General Population; Genetic; Genetic Transcription; Homeostasis; Hormones; Human; Inflammation; Inflammatory Bowel Diseases; Intestines; Ions; Knockout Mice; Life; Maintenance; Malignant Neoplasms; Mediating; Mucous Membrane; Mus; Nutrient; Organ; Organism; Parathyroid gland; Pathogenesis; Peptides; Phosphorylation; Play; Population; Process; Protein Dephosphorylation; Publishing; Receptor Activation; Receptor Signaling; Regulation; Role; Signal Pathway; Signal Transduction; Signal Transduction Pathway; Stimulus; Stratum Basale; Time; Tissues; Veterans; Wound Healing; base; beta catenin; cell type; colonic crypt; crypt cell; extracellular; gastrointestinal system; human disease; in vivo; intestinal homeostasis; member; migration; mouse model; novel; phospholipase C beta; prevent; protective effect; response; restoration

DESCRIPTION (provided by applicant): The sequential proliferation, lineage-specific differentiation, migration, and death of the epithelial cells of the colonic mucosa is a tightly regulated process modulated by a broad range of regulatory peptides, differentiation signals and luminal stimuli. Despite its fundamental importance for understanding the pathogenesis of human diseases, including inflammatory bowel diseases (IBD) and colorectal cancer (CRC), the signaling mechanisms involved remain incompletely understood. In this context, GTP-binding (G) protein-coupled receptors (GPCRs) and their intracellular signal transduction pathways play a critical role in the regulation of multiple functions of the digestive system, including cell proliferation, inflammation and promotion of CRC. The extracellular calcium-sensing receptor (CaSR), a member of the GPCR family, is prominently expressed by epithelial cells of the gastrointestinal (GI) tract but its function and mechanism in the regulation of normal and/or abnormal intestinal epithelial cell proliferation in vivo remains unknown. We demonstrated that CaSR stimulation by extracellular Ca2+ inhibits the proliferation of colon-derived epithelial cells. Our new preliminary studies obtained with a novel CaSR intestinal-specific knock out mouse show that the genetic ablation of the CaSR strikingly increases colonic crypt proliferation. Further preliminary results with colon-derived cells in culture demonstrate that CaSR stimulation strikingly decreases 2-catenin phosphorylation at Ser-552 and Ser-675, two amino acid residues that regulate 2-catenin localization and transcriptional activity. CaSR-mediated 2-catenin dephosphorylation at Ser-552 and Ser-675 coincided with its translocation from the nucleus to the plasma membrane and with 2-catenin-mediated transcription inhibition. Based on our preliminary results, the overarching hypothesis of this proposal is that CaSR signaling inhibits colon epithelial cell proliferation via down-regulation of b-catenin signaling. We plan to explore this hypothesis by pursuing the following Specific Aims: 1). Characterize the role of the CaSR in colon epithelial cell proliferation, differentiation, and cancer using a novel CaSR GI tract-specific knock-out mouse model; 2) Identify the signal transduction pathways that mediate the decrease in b-catenin phosphorylation at Ser- 552 and Ser-675 in response to CaSR stimulation in colon-derived epithelial cells. 3). Characterize b- catenin sub-cellular distribution and transcriptional activity in response to CaSR stimulation in colon- derived epithelial cells. We anticipate that the mechanistic studies proposed with genetically modified mice and human epithelial cells in culture will demonstrate that the CaSR inhibits colonic epithelial cell proliferation via negative crosstalk with the b-catenin signaling. These studies will also establish a robust rationale to explore protective effects of CaSR activation (e.g. via dietary Ca2+) in preventing CRC, one of the most common malignancies in the general population as well as in the US veteran population.

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