單次跨膜受體及其信號轉導
多種生長因子和細胞因子的受體為一類結構上為單次跨膜的糖蛋白。與七次跨膜受體(G蛋白偶聯型受體)相對應，將其稱為單次跨膜受體，即它們的跨膜區僅為單向一次性的，而不像七次跨膜受體那樣有反復的跨膜區段。
單次跨膜受體依照其結構特點可進一步分成多個家族和亞家族，其分類見表21－4及圖21-7。
圖21－17 各類單次跨膜受體的代表性舉例
| Receptor Type | Family | Examples | Characteristics |
| Protein-tyosine kinase receptors | PDGF receptor | PDGFR-α,PDGFR-βSCFR | Five immunoglobulin-like |
| family | (Kit),CSF-R(Fms),Flk-2 | domains extracellularly | |
| EGF receptor family | EGFR(ErbB),ErbB2(Neu),ErbB3,ErbB4 | Two cysteine-rich | |
| IGF receptor family | insulin R,IGF-1R | domains extracllularly | |
| HGF receptor family | HGFR(Met),MSPR(Ron) | Disulphide-bound heteroteramer of a and βchain | |
| VEGF receptor family | Flt-1,Flk-1(KDR) | Seven immunolobulin-like domains extracellularly | |
| Neurotrophin receptor family | Trk,TrkB,TrkC | ||
| Eph receptor family | Eph ,E1k,Eck,Cck5,Sek,Erk | Two FNIII-like domains and a cysteinerichdomain extracellularly | |
| Cytokine receptors | Class 1 cytokine receptor family | ||
| CH receptor subfamily | GHR,EPOR,PRLR,G-CSFR | Form homodimers | |
| IL-3 receptor subfamily | IL-3R,GM-CSFR,IL-5R | Form complexes with the cβ subunit | |
| IL-6 receptor subfamily | IL-6R,LIFR,CNTFR,IL-11R | Form complexs with gp 130 | |
| IL-2receptor subfamily | IL-2R,IL-2Rβ,IL-4R,IL-7R | Form complexes with il-2Rγ | |
| IFN-α/βR,IFN-γRα,IFN-γRβIL-10R | |||
| TNF receptor family | TNFR-1,TNFR-11MLNGFR,CD40,OX-40,Fas,CD27,CD30 | Form trimers | |
| Antigen receptors | TCR | Complex of α,β,γ,δ,ε,ζandηsubunits | |
| BCR | Complex of IgM and heterodimers ofα/βsubunits | ||
| Serine/threonine kinase receptor family | Type Ⅱ receptor family | TGFβR-Ⅱ,ActR-Ⅱ,ActR-ⅡB | Form hetero-oligomers with type Ireceptors,i, e,TGFβ-I,ActR-1,ActR-1B,BMPR-1A,BMPR-1B,ALK-1 |
Receptor families and subfamilies discussed in the text are presented .Abbreviations used: R, receptor; R, receptor; PDGF,platelet-derived growth factor; SCF, stem cell factor; CSF, colony-stimulationg factor; EGF,epidermal growth factor; FGF, fibroblast growth factor; IGF, insulin-like growth factor;HGF, hepatocyte growth factor;MSP,macrophage-stimulating protein;VEGF,vascular endothelial growth factor;FN,fibronectin; GH,growth hormone; EPO, erythropoietin; PRL, prolactin; IL, interleukin; LIF, leukemia inhibitory factor; CNTR, ciliary neurotrophic factore;IFN,interferon;TNF,tumor necrosis factor;Lngfr,low affinity nerve growth factor rcecptor;TCR,T ,cell rcecptor;BCR,B cell rcecptor;receptor;TGFR,transfoming growth factor βAct,activin;BMP,bone morphogenic protein,Alternative desingations are given within parentheses.
單次跨膜受體所介導的信號傳遞與轉換過程與G蛋白偶聯型受體介導的信號轉導有著很大差別。我們已經知道，G蛋白偶聯型受體所介導的主要是經由G蛋白的激活，然后作用于相應的效應分子，接下來最主要的是導致細胞內信使含量及分布的迅速改變從而調節靶分子的活性并改變細胞的功能狀態。單次跨膜受體介導的信號轉導過程則主要是蛋白分子的相互作用，并且有蛋白酪氨酸激酶的廣泛參與。對這些信號轉導途徑的了解在九十年代中取得了許多重要的進展。為跟蹤和理解這些信號轉導過程，我們首先需要知道參與這一過程的重要信號轉導分子和其中的一些特殊結構。
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