1、Classification of phosphatase according to the Amino acid sequence in active center,Ser/Thr phosphatase Tyr phosphatase Dual specificity,. G protein/small G protein,guanine nucleotide binding protein，G protein（鸟苷酸结合蛋白）亦称GTP结合蛋白a signal molecule in various pathways, functioning differently in differe
2、nt cells Two forms of G proteinG protein binding with GTP: its active formGTP hydrolysed to GDP: inactive form,2 types of G protein ：,Hetero-trimer G protein:（G）,(G)binding with receptor with 7 transmembrane dormains， Small G protein (21kD）,1. Hetero-trimer G protein mediated receptor signal directl
3、y,GG,Multiple Sites subunit with GTPase act.,Binding site with receptor Bingding site withsubunits GDP/GTP binding site Binding with dwonstream molecules,formed a complex with G,localized in regulate targeted protein directlyin mammalian,The activation/deactivation cycle for hormonally stimulated ad
4、enylate cyclase,G protein-coupled receptors，GPCRsLigand- GPCRs G protein-（AC,PLC)-cell function,The role of PIP2 in intracellular signaling,2. Ras surperfamily: important signal molecules,Small G protein （21kD），functioning as switch Ras is a first discoved G proteinRas family: each contains a GTPase
5、 domain,Factors control small G protein act.,Factor increasing act. ： guanine nucleotide exchange factor (GEF) guanine nucleotide release protein (GNRP) Factor decreasing act.： guanine nucleotide dissociation inhibitor (GDI)GTPase activation protein (GAP),Ras activation and its regulators,GTP,GDP,Ra
6、s,Ras,SOS,GAP,on,off,Summary of Section 3,Proteins are the main components of signaling pathways Proetin kinases and phosphotases are the switch in signaling pathways. G protein and small G protein are function as their binding with GTP/GDP,Section 4,The Structural Basis of Signal Transduction Netwo
7、rk 细胞信号转导网络的结构基础,. Signaling Complex and its character,Proteins wont separated each other in cellsbut aggregated Protein complex-functioning in life,1. Signaling complex ensures the efficiency, precision, variety,Priority:, directly contact，efficency, precision amplification collaboration, variety c
8、omplex, multiple,2. Signaling complex exists at membrane and cytoskeleton structure,Protein complex existed in membrane structure or cell skeleton compartmentation。,Advantage,由于已经有相对固定的分子作为集合目标存在，有利于信号转导分子很快找到结合伴侣，因此复合体转导效率要高于一个完全自由扩散的系统； 在形成信号转导复合体时，转导分子将以有序的方式依次进入复合体，因此信号转导的准确性会高于自由扩散系统。,3. Compon
9、ents of complex changes depended on exogenous signals,Dynamic state: the components and formation of signal complex depended on exogenous signals Significance:withdrew ligand - stop signaing immediately reutilization of signal molecules, save energy,. Domain is substantial basis of protein-protein i
10、nteraction,protein interaction domain,1. prot-prot interaction mediated by domains,Character of protein interaction domain (PID), one molecule contains two PID same domain existed in various proteins, but sequence are not exactly same binding specificity PID doesnt have enzyme activity,just binding,
11、Distribution and role of protein interaction domain,Domain and its recognized motif,2. Src homology 2 (SH2) domain,Src homology 2 domain: SH2 domianFunction: the recognized motif is phosphorylated tyrosine and neighboring amino acids Different protein contains different SH2- selectivity,3. SH3 Domai
12、n,Src homology 2 domain: SH3 domian Function: the recognized motif is proline-rich (9-10 Pro) sequence,4. PH Domain recognizes the phospholipids,PH domain in pleckstrin in platelet，so called pleckstrin homology PH binding with membrane PL derivative，make its localization to membrane, enzyme activity
13、 increase PH is a basic structure of prot-prot, prot-lipid interaction,. adaptor proteins and scaffolding proteins,adaptor protein a kind of mediator protein, Link one, upstream prot., to another, downstream role：recruit and organize the complex Most adaptor proteins contain two domains, no other sp
14、ecial domain,1. adaptor protein,Adaptor protein Nck,SH2,C,N,SH3,SH3,SH3,HGFR, VEGFR, BCR-Abl PDGFR, EphB1,SLP-76, HPK1, p130cas IRS-1,p62doc,CKIg2,WASP,IRS-1, DOCK180, NIK,IRS-1,DOCK180, Sos, NIK,Pak1,Pak3,NAP4,WIP,dynamin, synaptojanin、 Abl,c-Cbl,Abl,c-Cbl,NAP1,Sam68,2. Scaffolding proteins ensures
15、 the efficiency and specificity,Scaffolding proteins: large MW, binding with many signal molecules in same pathway Significance keep the related molecules gather together, keep specificity, not across to with other pathway Scaffolding proteins increase or decrease the activity of signaling create th
16、e complex and variety in signaling pathway,Sumaary of Section 4,Signaling complex exists at membrane and cytoskeleton structure. Within complex the special domain in a protein is a base of interacting with others.Adaptor proteins and scaffolding proteins are the linker molecules in signaling and net
17、work.,Section 5,General Signal Pathways Mediated by Membrane Receptors 膜受体介导的基本信号转导通路,3 types of membrane bound receptor：,Ion channel receptor (ICR) G-protein coupling receptor (GPCR) Single transmembrane receptor (STMR),Characters of 3 types receptors,. Ion Channel Receptor,structurally a channel,
18、open or close pass through ion, ligand-gated receptor channel Ligand: neurotransmitter mainly,Acetyl choline receptor,Acetylcholine Binding Site,Ion channel,overlook,side look,The role of Acetylcholin,Ion channel memb. electric potential change chemical signal formation cell function Ion channel Cat
19、ion channel: Acetyl Choline, Glutamic acid, 5-HydroxytrypotamineAnion channel: Glycine， -aminobutylic acid, . G-protein coupling receptor second messenger-target molecules,GPCR: binding G protein with tri-subunit activate G protein,GPCR a serpentine receptor, 7 transmembrane,1. G-protein activation
20、initiates signaling,Model of transduction via G-protein ：, ligand receptor binding receptor activates G-protein G-protein act. or inh. target prtoein change second messenger level or distribution, second messenger affects its target molecule conformational change,G-protein cycle,2. Activated G-prote
21、in alters activity of target mole.,活化的G蛋白的亚基主要作用于生成或水解细胞内第二信使的酶，如AC、PLC等效应分子（effector），改变它们的活性，从而改变细胞内第二信使的浓度。 可以激活AC的G蛋白的亚基称为s（s 代表stimulate）；反之，称为i（i代表inhibit）。,Ga subunit and its effect,3. Glucagon receptor - AC-cAMP-PKA pathways,Signals acts by AC-cAMP-PKA pathways,4. Angiotensin II receptor - P
22、LC-IP3/DAG-PKC,Angiotensin II receptor is a GCPR q PLC-IP3/DAG-PKC pathway,Signals acts by PLC-IP3/DG-PKC,此外，由于G蛋白亚型的不同，形成多种其他通路和效应，如PDE-cGMP-Na+通道信号转导通路、PLC-IP3-Ca2+/CaM-PK信号转导通路等。,. Enzyme coupling receptor-protein kinase kinase protein kinase target mole,酶偶联受体指那些自身具有酶活性，或者自身没有酶活性，但与酶分子结合存在的一类受体。
23、这些受体大多为只有1个跨膜区段的糖蛋白，亦称为单跨膜受体。 酶偶联受体种类繁多，但是以具有PTK活性和与PTK偶联的受体居多。,常见的酶偶联受体：,受体型蛋白酪氨酸激酶（receptors tyrosine kinases，RTKs） 蛋白酪氨酸激酶偶联受体（tyrosine kinase-coupled receptors，TKCRs） 受体型蛋白酪氨酸磷酸酶（receptors tyrosine phosphatases，RTPs） 受体型蛋白丝/苏氨酸激酶（receptors serine/threonine kinase，RSTK） 受体型鸟苷酸环化酶（receptors guanyl
24、ate cyclases，RGCs）,酶偶联受体大部分是生长因子和细胞因子的受体，它们所介导的信号转导通路主要是那些调节蛋白质的功能和表达水平、调节细胞增殖和分化。,1. PTK coupling receptor : similar model,PTK coupling receptor主要通过蛋白质相互作用激活自身或细胞内其他的PTK或丝/苏氨酸激酶来转导信号。 PTK偶联受体介导的信号转导途径的基本模式 ：,结合配体后受体形成二聚体或寡聚体； 第一个蛋白激酶被激活。对于具有蛋白激酶活性的受体来说，此步骤是激活受体胞内结构域的蛋白激酶活性；对于没有蛋白激酶活性的受体来说，此步骤是受体通过蛋
25、白质-蛋白质相互作用激活与它紧密偶联的蛋白激酶； 通过蛋白质-蛋白质相互作用或蛋白激酶的磷酸化修饰激活下游信号转导分子，通常是继续活化下游的一些蛋白激酶； 蛋白激酶通过磷酸化修饰激活代谢途径中的关键酶、反式作用因子等，影响代谢途径、基因表达、细胞运动、细胞增殖等。,表皮生长因子受体作用机制：,2. EGFR signaling pathway : RasMAPK,表皮生长因子受体（epidermal growth factor receptor, EGFR）是一个典型的受体型PTK。 RasMAPK途径是EGFR的主要信号通路之一。,EGFR介导的信号转导过程,3. Others pathwa
26、ys than enzyme couping receptor,T细胞抗原受体、B细胞抗原受体、肥大细胞表面的IgE受体,属于酶偶联受体，它们自身不具备蛋白酪氨酸激酶活性； 非受体型的Src家族蛋白酪氨酸激酶和ZAP70家族蛋白酪氨酸激酶是这一类受体的直接信号转导分子。 下游分子包括PLC、MAPK家族的活化，并有多种衔接蛋白参与。,大部分白细胞介素（interlukin, IL）受体属于酶偶联受体。,通过JAK（Janus Kinase）-STAT（signal transducer and activator of transcription）通路转导信号。 细胞内有数种JAK和数种STA
27、T的亚型存在，分别转导不同的白细胞介素的信号。,白介素介导的信号转导途径,转化生长因子（transform growth factor , TGF）受体,属于单次跨膜受体，自身具有蛋白丝氨酸激酶催化结构域。 受体活化后通过信号分子Smad介导的途径调节靶基因转录，影响细胞的分化。 细胞内有数种Smad存在，参与TGF家族不同成员（如骨形成蛋白等）的信号转导。,TGF消信号转导示意图,在细胞信号转导过程中，信号迅速发生并迅速终止，反应过程具有级联放大效应。 细胞内的信号转导系统具有通用性；细胞内一些信号转导分子和信号转导通路需要为不同的受体所共用，但是各种细胞又有其特殊的方式严格控制信号转导的特
28、异性流向。,影响细胞可以对外源信息做出特异性反应的因素包括：细胞间信息分子的浓度、相应受体的分布与含量、细胞内信号转导分子的种类和含量等。 不同组织可以以不同的方式使用同一信号转导分子，但是相互作用的分子可以不同，蛋白激酶的底物也可能不一样，从而导致输出信号的差别。,Summary of section 5,Ion Channel Receptor G-protein coupling receptor is a serpentine receptor and following as second messenger-target molecules Cascade of Enzyme co
29、upling receptor: Enzyme coupling receptor-protein kinase kinase protein kinase target mole,Human beta-adrenoreceptor,Integrins are not monomers. They mediate their biological function through heterodimer formation and ligand binding.,Solely overexpressed 1 subunit might induce the expression of certain subunit before it could have growth-inhibitory effect.,
