Multicellular Organisms have BIG Communication Problems ? Hey You – divide now!!! Oi! We need some glucose! Come in #7, your time is up! Will you PLEASE stop dividing!

Chapter 6 Signal Transduction

Cell communication and cell recognition Cell communication …. Cell recognition Cell signal …. Cell receptor …. intercellular receptor signal pathway cell surface receptor signal pathway ….. Integrin protein pathway Network signal and signal characteristics Signal pathway Signal Transduct ion

2001 L. H. Hartwell, R. T. Hunt, P. M. Nurse M&P key regulators of the cell cycle 2002 S. Brenner, H. R. Horvitz, J. E. Sulston M&P Apoptosis Nobel prizes awarded for research in signal transduction

6.1 cell communication and cell recognition Cell communication a Secret chemical signal a Secret chemical signal b Contact-depend signal( 接触性依赖的通讯） b Contact-depend signal( 接触性依赖的通讯） c Gap junction signal c Gap junction signal

Endocrine signaling – signaling molecules act on target cells distant from their site of synthesis by cells of endocrine organs Paracrine signaling – signaling molecules released by a cell only affect target cells in close proximity Autocrine signaling – cells respond to substances that they themselves release, same cell type chemical snaptic Neuronal signaling The Secret chemical Signal

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6.1.2 cell recognition cell recognition 细胞通过其表面受体与胞内信号物质选择性结合， 导致胞内一系列生理生化变化，最终表现为细胞整 体的生物学效应 细胞通过其表面受体与胞内信号物质选择性结合， 导致胞内一系列生理生化变化，最终表现为细胞整 体的生物学效应 Cells selectively bind with intercellular signal by cell surface receptor,trigger a series of physiological and biochemical changes, result in integrated cell effect

Signal transduction An extracellular signal can produce a change in the intracellular state of the cell without the initial signal crossing the membrane.

6.1.3 Cell signal Classify by chemical characteristic Hydrophobic signal （菑类激素；甲状腺 素 )can transport through cell membrane,bind with receptor in cytoplasm and nucleus to form complex Hydrophobic signal （菑类激素；甲状腺 素 )can transport through cell membrane,bind with receptor in cytoplasm and nucleus to form complex Hydrophilic signal, cannot transport through cell membrane,bind with cell surface receptor and produce second signal,this process called signal transduction Hydrophilic signal, cannot transport through cell membrane,bind with cell surface receptor and produce second signal,this process called signal transduction. Gaseous signal NO

In response to a signal from nerve cells, endothelial 内皮细胞 cells that line blood vessels make and release nitric oxide. Nitric oxide enters muscle cells in the vessel wall causing them to relax and dilate ( 扩大的 ) Blood flow increases and more oxygen can reach organs such as the heart. The 1998 Nobel prize was awarded to two U.S. scientists for discovering this mechanism. Gaseous signal :Nitric Oxide

 Nitric Oxide and Carbon Monoxide ◆ The nitric oxide (NO) is a major paracrine signaling molecule in the nervous, immune, and circulatory systems. NO is able to diffuse directly across the plasma membrane of its target cells. The molecular basis of NO action, however, is distinct from that of steroid action; rather than binding to a receptor that regulates transcription, NO alters the activity of intracellular target enzymes. ◆一氧化氮是可溶性的气体，产自精氨酸，在一些 组织中作为局部介质起作用。 NO 能够引起血管 壁的平滑肌细胞松弛

NO

classify by signal location Extracellular Extracellular Receptors which have N terminal face outwards and C terminal inside the cell.Receptors which have N terminal face outwards and C terminal inside the cell. When bound to a signal molecule, changes its conformationWhen bound to a signal molecule, changes its conformation Signal molecules are specific to their receptorsSignal molecules are specific to their receptors

Intercellular Intercellular Mostly triggered by the extracellular signalMostly triggered by the extracellular signal Which converts the extracellular into an intracellular signalWhich converts the extracellular into an intracellular signal Eg. - G protein, GTPase, cAMP, Ca++, Kinases, phosphatases and many moreEg. - G protein, GTPase, cAMP, Ca++, Kinases, phosphatases and many more Also called as second messengersAlso called as second messengers

6.1.4 Second messenger and molecular switch Second messenger: Primitive signal bind with receptor and then trigger second messenger （ cAMP,IP3,DG,) Primitive signal bind with receptor and then trigger second messenger （ cAMP,IP3,DG,)

第二信息至少有两个特征 : 第二信息至少有两个特征 : 是第一信息同其膜受体结合后最早在细胞膜内侧 或胞浆中出现，仅在细胞内部起作用的信息分子 是第一信息同其膜受体结合后最早在细胞膜内侧 或胞浆中出现，仅在细胞内部起作用的信息分子 能启动或调节细胞内稍晚出现的反应。 能启动或调节细胞内稍晚出现的反应。 目前公认的第二信息有 cAMP 、 DG 、 IP 3 、 cGMP 和 Ca 2+ 目前公认的第二信息有 cAMP 、 DG 、 IP 3 、 cGMP 和 Ca 2+

Molecule switch protein Protein kinase phosphorylation let it open ， Protein kinase phosphorylation let it open ， Dephosphorylation let it close Dephosphorylation let it close Protein+GTP=active Protein+GTP=active Protein+GDP=INactive Protein+GDP=INactive

Communication by extracellular signals steps : 1)Synthesis and release of signaling molecules by the signaling cell 2) Transport of the signal to the target cell 3) detection of the signal by a specific receptor protein 4) And change in cellular metabolism or gene expression triggered by the receptor- signaling molecule complex 5) Removal of the signal, often terminating the cellular response

6.2 Cell receptor Receptor: recognition and selectively bind with ligand signal, extracellular siganl change into intercellular physical or chemical signal ， triggered a series of process ， result in biological effect Receptor: recognition and selectively bind with ligand signal, extracellular siganl change into intercellular physical or chemical signal ， triggered a series of process ， result in biological effect Membrane Receptor intracellular receptor cell surface receptor Nucleus receptor Cell receptor

ReceptorsReceptors Signal molecules that do not enter the cell bind to cell- surface receptors. Signal molecules that do not enter the cell bind to cell- surface receptors. Signal molecules that enter the cell bind to intracellular receptors. Signal molecules that enter the cell bind to intracellular receptors.

intracellular receptor Transmembrane receptors Transmembrane receptors That span the thickness of the plasma membrane That span the thickness of the plasma membrane Intracellular domain and extracellular domain Intracellular domain and extracellular domain Signal trasduction/through small molecules (Ca++) – Ion Channels Signal trasduction/through small molecules (Ca++) – Ion Channels

intracellular receptor

Three classes of cell-surface receptors Ion-channel-linked receptors open an ion channel in response to the signal molecule. Ion-channel-linked receptors open an ion channel in response to the signal molecule. G-protein-linked receptors activate an intracellular G-protein that in turn activates intracellular enzymes. G-protein-linked receptors activate an intracellular G-protein that in turn activates intracellular enzymes. Enzyme-linked receptors directly activate a membrane bound enzyme. Enzyme-linked receptors directly activate a membrane bound enzyme.

Nuclear receptors Nuclear receptors Soluble proteins localised within the cytoplasm or the nuceloplasm Soluble proteins localised within the cytoplasm or the nuceloplasm Ligand activated trascription activators Ligand activated trascription activators Hormone regulation Hormone regulation Steroid receptors (located within cytosol Steroid receptors (located within cytosol

Defining a Receptor Specificity – a receptor must be able to distinguish between often closely-related signals High affinity – signals are often present in low concentrations – effective receptors can often detect nM to pM concentrations Saturability – a cell has a finite number of receptors and, thus there is a limit to the number of ligand molecules a cell can bind

Reversibility – ligand-receptor association is not covalent – as the ligand concentration drops the complex can dissociate Coupling – the receptor transfers a signal from ligand to cell

Coping with Multiple Signals – Receptor ‘Crosstalk’ Suppose a cell receives two signals. Signal A inhibits proliferation, whilst signal B stimulates proliferation… AB kinase Signal A activates a kinase… …which phosphorylates and inactivates the receptor for signal B - result – no proliferation

If ‘crosstalk’ only works in one direction (A to B) then signal A will be dominant If ‘crosstalk’ works in both directions, the outcome will depend on several factors e.g. Timing of signal perception Relative receptor density Relative signal concentration

6.3 intercellular receptor signal pathway 6.3 intercellular receptor signal pathway 亲脂小分子与细胞内受体结合 亲脂小分子与细胞内受体结合 细胞内受体的本质是激素激活的基因调控蛋 白，构成细胞内受体超家族 细胞内受体的本质是激素激活的基因调控蛋 白，构成细胞内受体超家族

steroid hormone( 甾类激素 ) signal pathway primary response secondary response

6.4 cell surface signal pathway A Ion-channel-linked receptors open an ion channel in response to the signal molecule. B G-protein-linked receptors activate an intracellular G-protein that in turn activates intracellular enzymes. activate an intracellular G-protein that in turn activates intracellular enzymes. C Enzyme-linked receptors directly activate a membrane bound enzyme.

A (ion-channel-linked receptor) Types of ion channel

1994 Nobel prize. Discovery of G-protein coupled receptors and their role in signal transduction 1994 Nobel prize. Discovery of G-protein coupled receptors and their role in signal transduction 43,409 articles in Medline that mention G proteins. 43,409 articles in Medline that mention G proteins. G  ＋ GTP 激活态（ open ） G  ＋ GTP 激活态（ open ） G  ＋ GDP 失活态（ close G  ＋ GDP 失活态（ close B G protein -linked signal pathway

G-protein sructure G-protein-coupled receptors G-protein-coupled receptors C-AMP C-AMP G-protein-linked signal pathway G-protein-linked signal pathway

   4 subtypes binds GTP activation of 2 nd mess. less variability also activates 2 nd mess.    G-protein sructure （ G-protein subunits ）

G  i/o   GsGsGsGs   GqGqGqGq   G  12/13   inhibition of cAMP production inhibition of Ca 2+ channels activation of GIRK K + channels G-protein subtypes increased synthesis of cAMP activation of Ca 2+ and K + channels activation of PLC  leading to activation of PKC (DAG) intracellular Ca 2+ release (IP 3 ) mediates signalling between GPCRs and RhoA (GTPase) function under investigation

1. Basic facts about G proteins 1. Basic facts about G proteins Each G-protein consists of 3 sub-units, sub-units can be together or separated.Each G-protein consists of 3 sub-units, sub-units can be together or separated. Each G-protein has a binding site that can be occupied by either GDP or GTP.Each G-protein has a binding site that can be occupied by either GDP or GTP. A G-protein is said to be inactive when it is bound to GDP.A G-protein is said to be inactive when it is bound to GDP. A G-protein is said to be active when it is bound to GTP.A G-protein is said to be active when it is bound to GTP.

Small GTP-binding proteins  Ras (growth factor signal cascades).  Rab (vesicle targeting and fusion).  ARF (forming vesicle coatomer coats).  Ran (transport of proteins into & out of the nucleus).  Rho (regulation of actin cytoskeleton)

GGGG   L Effector G-proteins Signal exterior cytosol

Extracellular Cytoplasmic COOH - -NH2 C1C1 C2 C3C3 e1 e2 e3 TM1 TM2TM3TM4TM5TM6TM7 D R Y G-protein-coupled receptors G-protein-coupled receptors -S-S- 与配体结合 G 蛋白作用部位

cAMP ATP  cAMP + PPi

Cyclic AMP  Cyclic-AMP is suited to be a transient signal.  Synthesis & degradation of cAMP are both spontaneous, but enzymes are required to synthesize these reactions.  Enzymes that synthesize and degrade cAMP are regulated.

 C-1 CAMP signal pathway C-1 CAMP signal pathwayC-1 CAMP signal pathway  C-2 磷脂酰肌醇信号通路 (Double messenger pathway) 磷脂酰肌醇 G-protein-linked signal pathway

Subunit of cAMP Rs and Ri GS and Gi CAMP enzyme

PKA GENE EXPRESXSION

cAMP activate cAMP-depend PKA

protein kinase A transcription factor CREB (CRE-binding protein) expression of cAMP- inducible genes.

CAMP 途径的信号解除和抑制  信号解除 ●通过磷酸二酯酶将 cAMP 降解, 形成 5'-AMP ；  信号抑制 ●通过抑制型的信号作用于 Ri, 然后通过 Gi 起作用

PIP2-DG pathway

PKC 是 Ca ² ⁺ 依赖性的，有两个功能区： 是 Ca ² ⁺ 依赖性的，有两个功能区： 一个是亲水的催化活性中心， 一个是亲水的催化活性中心， 另一个是疏水的膜结合区。 另一个是疏水的膜结合区。 在未受到刺激的细胞中， PKC 以非活性形式分布 于细胞溶质中，当细胞接受外界信号时， PIP ₂ 水 解，细胞内 Ca ² ⁺ 浓度的升高，引起从胞质转移到 细胞膜上而成待活状态，质膜上 DG 瞬间积累，使 PKC 与 Ca ² ⁺ 的亲和力增加，而处于活化状态。 在未受到刺激的细胞中， PKC 以非活性形式分布 于细胞溶质中，当细胞接受外界信号时， PIP ₂ 水 解，细胞内 Ca ² ⁺ 浓度的升高，引起从胞质转移到 细胞膜上而成待活状态，质膜上 DG 瞬间积累，使 PKC 与 Ca ² ⁺ 的亲和力增加，而处于活化状态。

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信号的终止  DAG 信号的解除 DAG 只是由 PIP 2 水解得到的暂时性产物, 寿命只有几秒钟, 靠两种方式进行降解 : DAG 只是由 PIP 2 水解得到的暂时性产物, 寿命只有几秒钟, 靠两种方式进行降解 : ◆被 DAG 磷酸激酶磷酸化, 生成磷脂酸 (PA),PA 被转化为 CMP- 磷脂酸, 再与肌醇作用合成磷 脂肌醇 (PI) 。 ◆ DAG 被 DAG 酯酶水解生成单脂酰甘油, 再进 一步水解成自由的多不饱和脂肪酸和花生四 烯酸甘油。

 of IP 3  Removal of IP 3 ◆ IP 3 hydrolyzation 在 5’ 磷酸酶的作用下, 水解为 I(1,4)P 2, 并进 在 5’ 磷酸酶的作用下, 水解为 I(1,4)P 2, 并进 一步水解成肌醇。 5’ 磷酸酶是一种膜结合的酶。 ◆在胞浆的肌醇磷酸脂 3- 激酶的作用下 IP 3 被磷 酸化成 I(1,3,4,5)P 4 。

 Ca 2+ 信号解除 ? ● IP 4 参与打开细胞质膜上的 Ca 2+ 通道, 使细胞质中 的 Ca 2+ 较为持久地增高。 ●胞内 Ca 2+ 浓度持久地升高, 可激活 Ca 2+ -ATP 酶 （质膜、内质网膜的钙泵），从而降低胞质中的 Ca 2+ ，使胞质中的 Ca 2+ 迅速恢复到基态水平 (10 -7 M), 并使活性 CaM- 酶复合物解离, 从而酶失去活 性, 细胞反应终止。

C Enzyme linked receptor  RTK-RAS pathway Other enzyme –linked receptor

RAS+GDP GRF GAP RAS+GTP

MAP : 有丝分 裂原活化 蛋白 MAPKKK: MAP 激酶的激酶的 激酶 MAPKKK: MAP 激酶的激酶的 激酶 MAPKK: MAP MAPKK: MAP 激酶的激酶 激酶的激酶 MAPK: MAP 激 酶 MAPK: MAP 激 酶

 Ras 蛋白信息传递途径 ◆ Ras 是原癌基因的表达产物； ◆介导： 细胞外信号 → 受体 →Ras→Rafl→MAPKKK 细胞外信号 → 受体 →Ras→Rafl→MAPKKK →MAPKK (MEK)→MAPK ，转录因子 → 激活 靶基因 → 细胞应答和效应。 →MAPKK (MEK)→MAPK ，转录因子 → 激活 靶基因 → 细胞应答和效应。 ◆该通路与 EGF 受体有关，并且有一中介蛋白 参与

Ras switch

SUMMARY Receptor tyrosine kinases (RTKs), which bind to peptide/protein hormones, may exist as dimers or dimerize during binding to ligands. Ligand binding leads to activation of the kinase activity of the receptor and autophosphorylation of tyrosine residues in its cytosolic domain. The activated receptor also can phosphorylate other protein substrates. Ras is an intracellular GTPase switch protein that acts downstream from most RTKs. SUMMARY Receptor tyrosine kinases (RTKs), which bind to peptide/protein hormones, may exist as dimers or dimerize during binding to ligands. Ligand binding leads to activation of the kinase activity of the receptor and autophosphorylation of tyrosine residues in its cytosolic domain. The activated receptor also can phosphorylate other protein substrates. Ras is an intracellular GTPase switch protein that acts downstream from most RTKs. RTKs are linked indirectly to Ras via two proteins, GRB2 and Sos RTKs are linked indirectly to Ras via two proteins, GRB2 and Sos

The SH2 domain in GRB2, an adapter protein, binds to specific phosphotyrosines in activated RTKs. The two SH3 domains in GRB2 then bind Sos, a guaninenucleotide exchange factor, thereby bringing Sos close to membrane-bound Ras · The SH2 domain in GRB2, an adapter protein, binds to specific phosphotyrosines in activated RTKs. The two SH3 domains in GRB2 then bind Sos, a guaninenucleotide exchange factor, thereby bringing Sos close to membrane-bound Ras · Binding of Sos to inactive Ras causes a large conformational change that permits release of GDP and binding of GTP. Binding of Sos to inactive Ras causes a large conformational change that permits release of GDP and binding of GTP. Normally, Ras activation and the subsequent cellular response is induced by ligand binding to an RTK. Normally, Ras activation and the subsequent cellular response is induced by ligand binding to an RTK.

6.5 Integrin protein pathway 6.5 Integrin protein pathway 整联蛋白是细胞表面的跨膜蛋白包括纤连蛋 白，胶原，和蛋白聚糖 整联蛋白是细胞表面的跨膜蛋白包括纤连蛋 白，胶原，和蛋白聚糖 粘着斑功能：机械结构功能；信号传递功能 粘着斑功能：机械结构功能；信号传递功能 细胞表面到细胞核的信号通路 细胞表面到细胞核的信号通路 细胞表面到细胞质核糖体的信号通路 细胞表面到细胞质核糖体的信号通路

6.6 Network signal and signal characteristics 6.6 Network signal and signal characteristics A Basic points of signal transduction 多途径多层次，具备收敛和发散特点 多途径多层次，具备收敛和发散特点 既有专一性又具备作用机制的相似性 既有专一性又具备作用机制的相似性 信号可以有控制的适度放大 信号可以有控制的适度放大 具备进行适应的特点 具备进行适应的特点 逐渐降低表面受体的数目 逐渐降低表面受体的数目 快速钝化受体 快速钝化受体 B 蛋白激酶的网络整合信息

interaction of Signal pathway interaction of Signal pathway

Signal transduction across the plasma membrane can cause a cascade of events that amplify the signal and distribute it to influence several cell processes in parallel.

Why do cells communicate? During development, cells differentiate to adopt specialized roles. Cells need to know whether to live, die, or divide. Neurotransmission. Regulation of metabolism. Contraction-expansion. Secondary sexual characteristics.

Cell Communication Why do cells communicate? How are signals transmitted between cells?