Aberrant Cell Signaling and Related Diseases

1. Aberrant Cell Signaling and Related Diseases Jimin Shao (邵吉民) Department of Pathology and Pathophysiology shaojimin@zju.edu.cn

2. Contents • Overview of cell signaling and signal transduction pathways • Disorders of signal transduction and mechanisms of diseases

3. Overview of cell signaling and signal transduction pathways 1.Cell Signaling (1) Direct Intercellular Communication (Gap Junction) • Connexins are four-pass transmembrane proteins • Six of connexins assemble to form a connexon • ~ 20 different isoforms of connexins in humans and mice

4. (2) Signaling by plasma-membrane bound molecules Mahoney KM, Rennert PD, Freeman GJ. Combination cancer immunotherapy and new immunomodulatory targets. Nat Rev Drug Discov. 2015;14(8):561-84

5. (3) Receptor-Mediated Intercellular communication (Cell-surface / Nuclear receptors )

6. (4) Communication by Extracellular Vesicles(EVs) Tkach, M. and C. Thery. Communication by Extracellular Vesicles: Where We Are and Where We Need to Go. Cell 2016;164(6): 1226-1232. Figure 1. EV-Mediated Effects Promoting Tumor Growth, Invasiveness, and Metastasis

7. 2. Receptor-Mediated Signal Transduction Systems • Cell Surface Receptors: - Ion Channel Linked Receptors - G-protein Coupled Receptors (GPCR) - Enzyme Linked Receptors Receptor tyrosine kinases (RTK) Tyrosine-kinase-associated receptors Receptor serine/threonine kinases Receptor guanylyl cyclases etc. - Others • Nuclear Receptors: - Steroid Receptors - Retinoid Receptors - Orphan Receptors

9. 3. General process for transmembrane signal transduction • Synthesis and secretion of signaling molecules (Ligands) • Receptor binding and transmemberane signal transduction • Intracellular signaling pathway • Regulation of cellular metabolism, function, gene expression, etc. • Down-regulation or termination of cellular responses

10. Herschkowitz JI, Fu X. MicroRNAs Add an Additional Layer to the Complexity of Cell Signaling. Science Signaling 2011.4 (184), jc5.

11. 4. Cell Signaling Functions Important signaling pathways and networks • Specific physiological functions for different cell types • Responses to stress • Interaction with microenvironment / other cells • Gene expression; Metabolism; Cell mobility • Cell fate regulation: Cell cycle, growth, differentiation, death

12. Disorders of signal transduction systems and Mechanisms of diseases (1) Causes: • Gene mutation-- Function loss or gain Changes of quality or activity of signal proteins • Epigenetic changes Changes of quantity of signal proteins • Autoimmune diseases • Secondary changes

13. (2) Pathogenesis: • Down-regulation / interruption of signaling • Signal Insufficiency (ligands) • Receptors down-regulation / desensitization: decreased quantity, binding affinity, inhibitory Ab, cofactor disorders, function loss, etc. • Defects in post-receptor pathways: adaptors, signal transducers, effectors (enzymes, transcription factors, etc) • Up-regulation / over-activation of signaling • Signal Excess • Receptor up-regulation, hypersensitivity, stimulatory Ab, etc • Signal transducers, TFs: over-expression, persistent activation • Others

14. 1. Aberrant Signal

15. (1) Aberrant Signal (Signal Insufficiency) • Insulin receptor (IR): heterotetramer (2, 2) • Insulin binding leads to change in conformation • Activates IR -subunit PTK activity • -subunit phosphorylates Tyr residues on cytoplasmic domains as well as downstream substrates (IRS) • Activates downstream pathways • Biological effects (glycogen synthesis, glucose transport and utilization, cell proliferation) Viral infections or other damages to pancreatic -cell insulin production decrease hyperglycemia Diabetes (Type I)

16. (2) Aberrant Signal (Signal Excess) ischemia, epilepsy, neurodegenerative diseases extracellular glutamate/aspartic acid NMDAR activation (N-methyl-D-aspartate receptor: Ion Channel Linked Receptor) Ca2+ influx activation of enzymes excitatory intoxication

17. 2. Aberrant Receptor in Cell Signaling

18. Disturbance of receptors can occur in: • Gene level: genetic or epigenetic changes; • Protein level: processes of protein synthesis, post-translational modification, conformation, oligomerization, translocation, endocytosis, degradation, etc. • Receptor alterations in number, structure, function, or regulation can result in: • Down-regulation: decrease in number of receptors • Desensitization: decreased response to ligand stimulation • Up regulation: increase in number of receptors • Hypersensitivity: increased response to ligand stimulation, or self-activation without ligands • Receptor diseases: Receptor alterations --- changes of ligand-receptor signaling --- abnormal cellular effects --- diseases

19. （1）Receptor Gene Mutation Genetic insulin-resistant diabetes: IR gene mutations Disturbances in synthesis transfer to the membrane affinity to insulin PTK activity proteolysis Type II Diabetes

20. Stimulatory Ab TSH-R（GPCR) 30~35 residues Gs Gq AC PLC cAMP DAG IP3 PKC Ca2+ Thyroid proliferation & secretion of thyroxine  hyperthyroidism (2) Autoimmune diseases - thyropathy Blocking Ab TSH-R 295~302 385~395 residues Binding of TSH to R ↓ hypothyroidism

21. Graves病（弥漫性毒性甲状腺肿） • 刺激性抗体模拟TSH 的作用 • 促进甲状腺素分泌和甲状腺腺体生长 • 女性>男性 • 甲亢、甲状腺弥漫性肿大、突眼 桥本病 (Hashimoto’s thyroditis,慢性淋巴细胞性甲状腺炎) • 阻断性抗体与TSH受体结合 • 减弱或消除了TSH的作用 • 抑制甲状腺素分泌 • 甲状腺功能减退、黏液性水肿

22. Heart failure, Myocardial hypertrophy • -adrenergic receptors (GPCR) down regulated or desensitized Reaction to catecholamines Myocardial contraction Alleviate Accelerate myocardial lesion heart failure (3) Secondary Abnormality in Receptors

23. Receptor diseases:

25. 3. Aberrant G-protein in Cell Signaling

26. Pituitarytumor: Gs gene mutation At Arg201 or Gln227 Hypothalamus GHRH Pituitary gland GHRH-R Gs Ac cAMP GH GTPase activity Persistent activation of Gs Persistent activation of AC cAMP Pituitary proliferation and GH secretion Acromegaly in adults Gigantism in children (1) G-protein gene mutation

28. Choleratoxin（霍乱毒素） intestinal epithelia Gs ribosylation at Arg201 Inactivation of GTPase Persistent activation of Gsand Ac, cAMP Secretion of chloride into the lumen, Inhibition of sodium uptake from the lumen, Large volumes of fluid into the lumen of the gut Diarrhea and dehydration Circulation failure (2) G-protein modification

29. 4. Aberrant intracellular Signaling • The intracellular signaling involves: various messengers, transducers, transcription factors, and etc. • Disorders can occur in any of these settings: -- Calcium overload is a general pathological process in various diseases; -- The level of NO is positively correlated with ischemic injury; -- Stimulation of NF-B is seen in various inflammatory responses; --Aberrant intracellular Signaling in carcinogenesis, and etc.

30. Multifactor Aberrancies in Cancer ---Enhancement of proliferating signals Ligands (GFs, e.g. EGF) Receptors (overexpression, activation of TPK, e.g. EGFR) Intracellular signal transducers： Ras gene mutation Ras-GTPase Ras activation Raf MEK ERK (MAPK) Proliferation TUMOR

31. TGF- + TGF-R PSTK activation Smad-phosphorylation P21/P27/P15 expression Cdk4 inhibition Cell cycle arrests Inhibits cell proliferation (pro-apoptosis) Gene mutation Negative regulation Cancers ---Deficits in proliferation-inhibiting signals

32. 5.Multiple Abnormalities in Signaling Pathways

33. Major signaling pathways relevant to cancer (Hanahan D, Weinberg RA. Cell 2011, 144:646) (Weinberg RA. the biology of cancer. 2013)

35. 6. Relationship between Stimulants and Pathological Effects --Same Stimulant Induces Different Responses (the same stimuli can act on different receptors) --Different Signals Induces the Same Pathologic Response (different receptors use the same pathway or by cross-talk)

36. 7. Principles for Treatment of Aberrant Signaling-related Diseases Stratagy: • Regulate the level of extracellular molecules • Regulate the structure and the function of receptors • Regulate the level and modifications of modification enzymes, messengers, signal transducers, transcription factors, effectors, etc Target therapy: • Breast cancer: EGFR overexpression –Herceptin (mAB) • Chronic myeloid leukemia (CML): Bcr-Abl (abnormal tyrosine kinase) — Gleevec (small compound inhibitor)

37. Inhibition of tumor growth by targeting downstream signaling elements

38. 教学目标: 1.细胞信号转导异常的基本原因和类型； 2.细胞信号转导障碍相关疾病发生发展的基本规律； 3.细胞信号转导在疾病靶点研究、临床诊疗中的应用。 思考题： 试述主要的细胞信号通路及其调节机制。 简述生长因子导致细胞增殖的信号转导过程。 受体异常有哪几种类型，举例相关疾病予以说明？ II型糖尿病中胰岛素受体有何异常？ 霍乱发生的分子机制。 举例说明肿瘤与信号转导异常的关系。 举例说明心血管疾病中的信号转导异常。 试述Graves病和桥本病发病机制的异同。 试述垂体腺瘤引起肢端肥大症机制。 举例说明G蛋白介导的细胞信号转导障碍性疾病的机制。