信号转导2-生化课05.ppt

Signal-Transduction Pathways (II) 郑利民 2005－12 珠海 PARTⅠ 1 Basic characteristics of signal transduction 2 Four general types of signal transducers PARTⅡ 1 Regulatory mechanisms 2 Some diseases caused by defects in the biosignaling pathways Regulatory mechanisms of Bio-signals 3.1 Phosphorylation as a regulatory mechanism 3.2 Regulation of transcription by steroid hormones 3.3 Regulation of the cell cycle by protein kinases Mechanisms by which hormones, retinoids, and Vit. D regulate gene expression 3.3.1 The cell cycle What is cell cycle? A process of cellular reproduction Cell cycle transits orderly and irreversibly Cell cycle transits orderly and irreversibly The completion of one phase is required for the beginning of the next. Periodic activation of specific cyclin-Cdk complexes A cycle of protein destruction eliminates proteins used in the preceding phase as well as proteins that would inhibit progression into the next phase. Cyclin-dependent kinases (Cdks) Cdks drive cell cycle progression by phosphorylating a group of substrates Regulation of Cdks activity Cyclin: Activating subunit. Cyclins were named because of their cyclic expression during the cell cycle Growth controlling signals are conveyed by stimulatory or inhibitory pathways CDKs Regulate Cell Division by Phosphorylating Critical Proteins some target proteins of CDKs: Laminin - Breakdown of nuclear envelope before segregation of sister chromatids in mitosis is partly due to Pi-laminin by CDK Actin myosin contractile machinery----Involved in pinching a dividing cell into two equal parts during cytokinesis Retinoblastoma protein, pRb--participates in a mechanism that arrests cell division in G1 3.3.3 Oncogenes, Tumor Suppressor Genes (TSGs), and Programmed Cell Death Oncogenes: encode defective signaling proteins ( e.g., growth factors, receptors, G proteins, protein kinases, or transcription regulators), continually giving the signal for cell division; TSG: encode regulatory proteins; no