细胞信号转导1

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4) Molecular complementary
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5) Effector specificity
• Same ligand
• Same receptor • Different cell type
• Different cellular response
• Example: different types of Ach receptors on skeletal muscle cells, heart muscle cells, and the pancreatic acinar cells.
Robert F. Furchgott 1/3 of the prize USA 1916 ~
Louis J. Ignarro 1/3 of the prize USA 1941~
Ferid Murad 1/3 of the prize USA 1936~
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• Robert F. Furchgott’s work EDRF (endothelium-derived relaxing factor)
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• Ferid Murad’s work
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• Louis J. Ignarro’s work
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• NO/cGMP pathway & relaxation of arterial smooth muscle
NOS-1: neural NOS-2: inducible NOS-3: endothelial
48 nuclear receptors
(human), 2 categories: classical endocrine hormones receptors and orphan receptors.
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Leabharlann Baidu
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4. Protein kinases and phosphatases
1) Phosphorylation and dephosphorylation: common cellular mechanism for regulating protein activity
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A simple signal transduction pathway involving one kinase and one target protein
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5. Intracellular second messengers
1) Second messengers
• The binding of ligands (first messengers) to many cellsurface receptors leads to a short-lived increase (or decrease) in the concentration of certain low-molecular-weight intracellular signaling molecules termed second messengers. Such as Ca2+ , cAMP, cGMP, DAG, IP3
Pathways involving proteolysis
Molecular Cell Biology，6th ed., H. Lodish, 2007
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2) Signaling molecules binding to intracellular receptors
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3) The steroid receptor superfamily
1) High affinity:
Receptor binds only a single signaling molecule or a group of structurally very closely related molecules.
2) High specificity:
The ability of receptors bind or not bind closely related substances.
NO binds to GC (guanylate cyclase, soluble form activated by NO, transmembrane form activated by ANF), CO also activates GC.
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2. Binding of signaling molecules activates receptors
cellular responses
• This chain of intermediates: a signal transduction pathway.
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1. Signaling molecules
1) Intercellular & intracellular signaling molecules
Signal Transduction and G Protein Coupled Receptors
Han Yingying Dept. of Biochemistry and Molecular Biology
Tel:69156428 E-mail:151259808@qq.com Sep.19 2014
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3) Measure the affinity of a receptor for its ligand a) Dissociation constant
• • Kd=[R][L]/[RL] Kd=[L] which half of the receptors have a ligand bound when the system at equilibrium
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6. Study the receptors and activity of signal transduction proteins
1) Purification of receptors
• • Recombinant DNA Affinity chromatography
2) Study the activity of signal transduction protein
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Part Ⅰ From extracellular signal to cellular response
• Signal transduction:
extracellular signaling molecules + cell-surface receptors
several intermediate proteins or small molecules
3) Desensitization
regulation at the levels of transcription, translation and posttranslational processing, controlling the rate of degradation.
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3. Cell-surface receptors & intracellular receptors
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2) Types of protein kinases and phosphatases
• About 600 protein kinases and 100 phosphatases • Two types of protein kinases: add phosphate to the hydroxyl group on tyrosine residues add phosphate to the hydroxyl group on sersine/threonine residues • The receptor possesses intrinsic kinase activity or tightly bound to a kinase.
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6) Maximal cellular response usually does not require activation of all receptors
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7) Sensitivity of a cell to external signals
1) The fewer receptors present on a cell, the less sensitive the cell is to the ligand. 2) Hypersensitivity (such as HER2)
＜108 mol/L
high affinity
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1) Eight classes of cell-surface receptors
Signaling via Enzyme -Linked Cell -Surface Receptor
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Molecular Cell Biology，6th ed., H. Lodish, 2007
• Intercellular signal molecules: proteins/peptides, amino acids, nucleotides, steroids, retinoids, FA, gas(NO, CO) • Intracellular signal molecules:
second messengers(cAMP, cGMP, DAG, Ca2+, IP3, etc), nuclear(third) messengers(steroids, retinoids, thyroxine, VD)
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b) Binding assays to determine the Kd
• For receptors have high affinity for their ligand
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• For low-affinity ligands
Low-affinity
Low-affinity
High-affinity
• • Immunoprecipitation of kinases Pull down assays of GTP-binding proteins
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Activation of three signal transduction proteins by phosphorylation
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A pull-down assay shows that the small GTPbinding protein Rac1 is
•
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Four common intracellular second messengers
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2) Advantages of second messengers
• Diffuse through the cytosol much faster than proteins • Facilitate amplification of extracellular signal
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Outline
• From extracellular signal to cellular response • Cell surface receptors and signal transduction proteins • G-protein coupled receptors (GPCRs): structure and mechanism • GPCRs that regulate ion channels • GPCRs that activate or inhibit adenylyl cyclase • GPCRs that trigger elevation in cytosolic Ca2+
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2) Signaling molecules act locally or at a distance
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3) NO and CO
The Nobel Prize in Physiology or Medicine 1998
"for their discoveries concerning nitric oxide as a signalling molecule in the cardiovascular system"