清华大学：《生物化学》课程PPT教学课件（英文版）General introduction Ion channels

Biosignaling Ye-Guang Chen

Biosignaling Ye-Guang Chen

General introduction Ion channels G-protein coupled receptors Second messengers Tyrosine kinase receptors From plasma membrane to the nucleus Regulation of gene expression Cytokine signaling Cell cycle Apoptosis Cell signaling and diseases

General introduction Ion channels G-protein coupled receptors Second messengers Tyrosine kinase receptors From plasma membrane to the nucleus: Regulation of gene expression Cytokine signaling Cell cycle Apoptosis Cell signaling and diseases

General introduction Ion channels G-protein coupled receptors Second messengers Tyrosine kinase receptors From plasma membrane to the nucleus Regulation of gene expression Cytokine signaling Cell cycle Apoptosis Cell signaling and diseases

General introduction Ion channels G-protein coupled receptors Second messengers Tyrosine kinase receptors From plasma membrane to the nucleus: Regulation of gene expression Cytokine signaling Cell cycle Apoptosis Cell signaling and diseases

table 13-1 Some Signals to Which Cells Respond Antigens Cell surface glycoproteins/oligosaccharides Developmental signals Extracellular matrix components Growth factors Hormones Light Mechanical touch Neurotransmitters Odorants Pheromones Tastants

Four features of signal transducing systems Part ll Structure and Catalysis (a)Specificity (c)Desensitization/Adaptation Signal molecule fits Receptor activation triggers binding site on its feedback circuit that shuts complementary receptor; off the receptor or removes Receptor other signals do not fit Receptor it from the cell surface Effect b)Amplification (d) Integration When enzymes activate When two signals have Signal 1 Signal 2 enzymes, the number of opposite effects on a affected molecules metabolic characteristic increases geometrically Enzyme 1 such as the concentration an enzyme cascade. of a second messenger x, Receptor or the membrane potential Vm, the regulatory outcome results from the integrated Enzyme input from both receptors.↑x] or Tv.↓ X)or V Ne△X]orVm R

Four features of signal￾transducing systems

intercellular signaling (a) Endocrine signalin (c) Autocrine signaling Blood vessel o Extracellular signal OO K Y Receptor Y Membrane-attached Hormone secretion signal into blood by endocrine gland Distant target cells Target sites on same cel (b)Paracrine signaling (d) Signaling by plasma membrane-attached proteins Secretory cell Adjacent target cell Signaling cell Adjacent target cel

General schemes of intercellular signaling

Gated ion channel Serpentine receptor Opens or closes in External ligand binding to receptor(r)activates an response to concentration intracellular GTP-binding of signal ligand (S) or membrane potential protein(G), which regulates an enzyme(Enz)that ates an intracellular Ion nd me X R Plasma Receptor enzyme membrane Ligand binding to stimulates enzyme activity in intracellular Steroid DNA Steroid binding to a nuclear receptor protein allows the mRNA ptor to regulat Nuclear the expression of envelope Protein specihc genes

Four general types of signal transducers

General introduction Ion channels G-protein coupled receptors Second messengers Tyrosine kinase receptors From plasma membrane to the nucleus Regulation of gene expression Cytokine signaling Cell cycle Apoptosis Cell signaling and diseases

General introduction Ion channels G-protein coupled receptors Second messengers Tyrosine kinase receptors From plasma membrane to the nucleus: Regulation of gene expression Cytokine signaling Cell cycle Apoptosis Cell signaling and diseases

transmembrane electrical potential 3 Na+ The electrogenic Na*K ATPase establishes the membrane potential Na*K+ ATPase Plasma membrane ADP+Pi INa 2K Lo [K+]Low High [Ca2+]High [CI] High lons tend to move down their electrochemical gradient across the polarized membrane

Transmembrane electrical potential

table 13-2 lon Concentrations in Cells and Extracellular fluids(mM) K Na Ca2+ In Out Out Out n Out Cell t Squid axon 400 20 50 440 ≤0.4 10 40-150 560 Frog muscle 124 2.3 10.4 109 <0.1 2.1 1.5 78