出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2013/08/02 17:23:03」(JST)
Cell Adhesion Molecules (CAMs) are proteins located on the cell surface[1] involved in binding with other cells or with the extracellular matrix (ECM) in the process called cell adhesion. Essentially, cell adhesion molecules help cells stick to each other and to their surroundings.
These proteins are typically transmembrane receptors and are composed of three domains: an intracellular domain that interacts with the cytoskeleton, a transmembrane domain, and an extracellular domain that interacts either with other CAMs of the same kind (homophilic binding) or with other CAMs or the extracellular matrix (heterophilic binding).
Most of the CAMs belong to four protein families: Ig (immunoglobulin) superfamily (IgSF CAMs), the integrins, the cadherins, and the selectins.
One classification system involves the distinction between calcium-independent CAMs and calcium-dependent CAMs.[2]
Immunoglobulin superfamily CAMs (IgSF CAMs) are either homophilic or heterophilic and bind integrins or different IgSF CAMs.
These are also known as addressins. Two well known examples are CD34 and GLYCAM-1.
Integrins are one of the major classes of receptors within the ECM[3] and mediate cell-ECM interactions with collagen, fibrinogen, fibronectin and vitronectin.[4] Integrins provide essential links between the extracellular environment and the intracellular signalling pathways which can play roles in cell behaviours such as apoptosis, differentiation, survival and transcription.[5]
Integrins are heterodimeric; as they consist of an alpha and beta subunit.[6] There are currently 18 alpha subunits and 8 beta subunits which combine to make up 24 different integrin combinations.[4] Within each of the alpha and beta subunits there is a large extracellular domain, a transmembrane domain and a short cytoplasmic domain.[7] The extracellular domain is where the ligand binds through the use of divalent cations. Generally Mn2+
increases affinity, Mg2+
promotes adhesion to cells and Ca2+
decreases cell adhesion.[5] Integrins regulate their activity within the body by changing conformation. Most exist at rest in a low affinity state which can be altered to high affinity through an external agonist which causes a conformational change within the integrin, increasing their affinity.[5]
An example of this is the aggregation of platelets;[5]
The cadherins are homophilic Ca2+
-dependent glycoproteins.[8] The classic cadherins (E-, N- and P-) are concentrated at the intermediate cell junctions which link to the actin filament network through specific linking proteins called catenins.[8]
Each cadherin exhibits a unique pattern of tissue distribution, such as epithelial (E-cadherins), placental (P-cadherins), neural (N-cadherins), retinal (R-cadherins), brain (B-cadherins and T-cadherins) and muscle (M-cadherins).[8] Many cell types express combinations of cadherin types.
The extracellular domain has major repeats called extracellular cadherin domains (ECD). Sequences involved in Ca2+
binding between the ECDs are necessary for cell adhesion. The cytoplasmic domain has specific regions where catenin proteins bind.[9]
The selectins are a family of heterophilic CAMs that bind fucosylated carbohydrates, e.g., mucins. The three family members are E-selectin (endothelial), L-selectin (leukocyte), and P-selectin (platelet). The best-characterized ligand for the three selectins is P-selectin glycoprotein ligand-1 (PSGL-1), which is a mucin-type glycoprotein expressed on all white blood cells.
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リンク元 | 「接着分子」 |
拡張検索 | 「cell adhesion molecule」「platelet endothelial cell adhesion molecule-1」「neuron-glia cell adhesion molecule」「intracellular adhesion molecule 1」 |
関連記事 | 「adhesion」「molecule」 |
グループ名 | 機能 | 名称 | 別名 | 組織分布 | リガンド | |
セレクチン | 炭化水素鎖に結合。 白血球-内皮細胞の反応を開始 |
P-selectin | PADGEN | CD62P | 活性化した内皮細胞、活性化した血小板 | PSGL-1, sialyl-Lewisx |
E-selectin | ELAM-1 | CD62E | 活性化した内皮細胞 | sialyl-Lewisx | ||
インテグリン | CAMや細胞外マトリックスに結合。 強い結合 |
LFA-1 | αL:β2 | CD11a:CD18 | 単球、T細胞、マクロファージ、好中球、樹状細胞 | ICAMs |
CR3, Mac-1 | αM:β2 | CD11b:CD18 | 好中球、単球、マクロファージ | ICAM-1, iC3b, fibrinogen | ||
CR4, p150.95 | αX:β2 | CD11c:CD18 | 樹状細胞、マクロファージ、好中球 | iC3b | ||
VLA-5 | α5:β1 | CD49d:CD29 | 単球、マクロファージ | fibronectin | ||
免疫グロブリンスーパーファミリー | 細胞結合で様々に働く。 インテグリンの基質 |
ICAM-1 | CD54 | 活性化した内皮細胞 | LFA-1, MAC1 | |
ICAM-2 | CD102 | 非活性化状態の内皮細胞、樹状細胞 | LFA-1 | |||
VCAM-1 | CD106 | 活性化した内皮細胞 | VLA-4 | |||
PECAM | CD31 | 活性化した白血球、内皮細胞間の結合 | CD31 |
名称 | 分布組織 | リガンド | ||
CD2 | LFA-2 | T細胞 | LFA-1 | CD53 |
ICAM-1 | CD54 | 活性化した血管、リンパ球、樹状細胞 | LFA-1, Mac-1 | |
ICAM-2 | CD102 | 非活性化状態の血管 | LFA-1 | |
ICAM-3 | CD50 | Naive T cells | DC-SIGN, LFA-1 | |
LFA-3 | CD58 | リンパ球、APC | CD2 | |
VCAM-1 | CD106 | 活性化した内皮細胞 | VLA-4 |
-接着分子
-細胞接着分子
-カドヘリン
血小板内皮細胞接着分子-1、血小板内皮細胞接着分子1
.