Aberrant Cell Signaling and the Related Disorders

1. Aberrant Cell Signaling and the Related Disorders Jimin Shao (邵吉民) Professor, Dept. Pathology and Pathophysiology Tel: 88208209 E-mail: shaojimin@zju.edu.cn

2. (1) Causes • Gene mutation-- Function loss or gain • Quantity change of signaling pathway proteins • Activity change of signaling pathway proteins • Autoimmune diseases • Secondary changes (2) Pathogenesis Abnormality: Ligands, Receptors, Post-receptor components, Effectors • Down-regulation / interruption of signaling • Signal Insufficiency • Receptors down-regulation/desensitization: decreased quantity, binding affinity, inhibitory Ab, cofactor disorders, function loss, etc. • Defects in Adaptors, Signal transducers, TFs, other Effectors, etc. Up-regulation / over-activation of signaling • Signal Excess • Receptor up-regulation, hypersensitivity, stimulatory Ab, etc • Signal transducers, TFs: over-expression, persistent activation, etc.

3. 1. Aberrant Signal

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

5. (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 [Ca2+], activation of enzymes excitatory intoxication

6. 2. Aberrant Receptor in Cell Signaling • Disturbance of receptors can occur in: • gene level, • Protein level: synthesis, post-translational modification, conformation, oligomerization, translocation, endocytosis, degradation, and etc. • Receptor alterations in number, structure, function, and regulation lead to: • 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

7. Insulin Activate IR(RPTK) IRS PI3K Ras/Raf/MEK/ERK Glu Transport & Utilization, Glycogen Synthesis, etc Cell proliferation （1）Receptor Gene Mutation Genetic insulin-resistant diabetes IR gene mutations Disturbances in synthesis transfer to the membrane affinity to insulin PTK activity proteolysis/degradation Type II Diabetes

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

9. 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

10. 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

11. 受体异常疾病

13. 3. Aberrant G-protein in Cell Signaling

14. 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 Acromegaly in adults Gigantism in children (1) G-protein gene mutation Pituitary proliferation and secretion

15. (2) G-protein modification Cholera toxin 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 volumns of fluid into the lumen of the gut Diarrhea and dehydration Circulation failure

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

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

18. 5.Multiple Abnormalities in Signaling Pathway

20. 6. Relationship between Stimulants and Pathological Effects • (1) Same Stimulant Induces Different Responses • (the same stimuli can act on different receptors) • (2) Different Signals Induces the Same Pathologic Response • (different receptors use the same pathway or by cross-talk)

21. (3) Different receptors use same pathways GPCR, RTK, Cytokines Rs PLC Ras PI-3K PKC Raf PKB MEK ERK

22. (4) Cross talk— how hypertension leads to myocardial hypertrophy? Mechanic stimuli GF TGF- NE, AT-II Na+, Ca2+ influx Na+-H+ exchange PLC TPK PSTK Ca2+/PKC Ras Smad-P Alkalization Raf MAPK Transcription factors, target genes Target proteins Myocardial Hypertrophy

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