Seltzer J L, Lee A Y, Akers K T, Sudbeck B, Southon E A, Wayner E A, Eisen A Z
Division of Dermatology, Washington University School of Medicine, St. Louis, Missouri 63110.
Exp Cell Res. 1994 Aug;213(2):365-74. doi: 10.1006/excr.1994.1211.
The matrix metalloproteinase 72-kDa type IV collagenase (also known as gelatinase A) is thought to be involved in both normal connective tissue remodeling and invasive pathological processes. Like other matrix metalloproteinases, 72-kDa type IV collagenase is secreted by fibroblast monolayers as an inactive proenzyme, but is unique among this enzyme family in that it is not activated by serine proteinases such as plasmin. However, when fibroblasts are cultured in a collagen lattice, a situation thought to better approximate in vivo conditions, we have invariably found much of the secreted 72-kDa type IV collagenase in its enzymatically active 62-kDa form. Although collagen lattice contraction appeared to be required for the activation of 72-kDa type IV collagenase, we have found that the process of contraction can be dissociated from proenzyme activation. Both cytochalasin D and alpha-methylmannoside completely blocked lattice contraction, but not proenzyme activation. Furthermore, the monoclonal antibody M-13, which is directed against the beta 1 integrin chain, blocked collagen lattice contraction but not 72-kDa type IV procollagenase activation. At concentrations significantly higher than required to block lattice contraction or cell adhesion to collagen, M-13 was able to inhibit proenzyme activation. A second monoclonal antibody to the beta 1 integrin, P5D2, had little effect on collagen lattice contraction at low concentrations, but could significantly inhibit the activation of 72-kDa type IV procollagenase. Antibodies to the integrin alpha 2 chain also inhibited proenzyme activation. These data show that the activation of 72-kDa type IV collagenase proenzyme, like collagen lattice contraction, is mediated by beta 1 integrin receptors, possibly alpha 2 beta 1. Although both anti-beta 1 antibodies used are directed to the same site on the integrin chain, the fact that each antibody preferentially blocks a different event, either lattice contraction or activation of 72-kDa type IV collagenase, suggests the existence of branch points in the receptor-mediated signal transduction pathway.
基质金属蛋白酶72-kDa IV型胶原酶（也称为明胶酶A）被认为参与正常结缔组织重塑和侵袭性病理过程。与其他基质金属蛋白酶一样，72-kDa IV型胶原酶由成纤维细胞单层作为无活性的酶原分泌，但在该酶家族中是独特的，因为它不会被诸如纤溶酶之类的丝氨酸蛋白酶激活。然而，当成纤维细胞在胶原晶格中培养时（这种情况被认为更接近体内条件），我们总是发现大量分泌的72-kDa IV型胶原酶呈其具有酶活性的62-kDa形式。虽然胶原晶格收缩似乎是72-kDa IV型胶原酶激活所必需的，但我们发现收缩过程可以与酶原激活分离。细胞松弛素D和α-甲基甘露糖苷都完全阻断晶格收缩，但不阻断酶原激活。此外，针对β1整合素链的单克隆抗体M-13阻断胶原晶格收缩，但不阻断72-kDa IV型前胶原酶激活。在浓度显著高于阻断晶格收缩或细胞与胶原粘附所需的浓度时，M-13能够抑制酶原激活。针对β1整合素的第二种单克隆抗体P5D2在低浓度时对胶原晶格收缩几乎没有影响，但能显著抑制72-kDa IV型前胶原酶的激活。针对整合素α2链的抗体也抑制酶原激活。这些数据表明，72-kDa IV型胶原酶原的激活与胶原晶格收缩一样，是由β1整合素受体介导的，可能是α2β1。虽然所使用的两种抗β1抗体都针对整合素链上的同一位点，但每种抗体优先阻断不同事件（要么是晶格收缩，要么是72-kDa IV型胶原酶激活）这一事实表明，在受体介导的信号转导途径中存在分支点。
