Leon O, Panos C
Infect Immun. 1985 Dec;50(3):745-52. doi: 10.1128/iai.50.3.745-752.1985.
Dried and wet mouse fibroblast monolayers with labeled collagenous substrate were used to study the effects of lipoteichoic acid (LTA) on cellular prolyl hydroxylase activity. LTA is a scavenger of cations, and Fe2+ is essential for prolyl hydroxylase activity. Surprisingly, addition of LTA to dried monolayers resulted in increased prolyl hydroxylase activity, whereas preincubation of Fe2+ with LTA only negated this increase. However, significant inhibition of enzyme activity by wet monolayers occurred whether LTA was added directly to the test system or whether it was used after preincubation with Fe2+. These data suggest that LTA causes membrane perturbations. Also, that the binding of LTA to the membrane of dried and wet monolayers appears to be decidedly different when based on the subsequent availability of Fe2+ for cellular prolyl hydroxylase activity. The ability of LTA to act as a cationic exchanger and the presence of intracellular Fe2+ inaccessible to LTA probably accounted for the lack of complete inhibition of prolyl hydroxylase activity by this amphiphile in the wet cell system. Considerably less iron was needed to negate the partial inhibition of prolyl hydroxylase activity by LTA in viable cells than was needed to restore the increased enzyme activity by this amphiphile in equivalent dried preparations. These and other results showed that, although LTA does not affect collagen polypeptide chain formation in wet monolayers, its involvement at the molecular level does result in a marked decrease in the hydroxylation of collagenous peptidyl prolyl residues through LTA interaction with Fe2+. This reduction in prolyl hydroxylase activity equaled the reduction in hydroxylation of collagenous protein in fibroblast monolayers caused by LTA reported earlier (O. Leon and C. Panos, Infect. Immun. 40:785-794, 1983). Therefore, these data suggest that partial inhibition of prolyl hydroxylase activity is directly related to the synthesis of defective collagen by wet fibroblast monolayers exposed to minute amounts of group A, type 12 streptococcal LTA. Use of LTA also showed that complete inhibition of hydroxyproline formation is not required for the continued formation and accumulation of defective collagenous protein by these monolayers.
用带有标记胶原底物的干燥和湿润小鼠成纤维细胞单层来研究脂磷壁酸（LTA）对细胞脯氨酰羟化酶活性的影响。LTA是阳离子清除剂，而Fe2+对脯氨酰羟化酶活性至关重要。令人惊讶的是，向干燥单层中添加LTA会导致脯氨酰羟化酶活性增加，而将Fe2+与LTA预孵育只会消除这种增加。然而，无论LTA是直接添加到测试系统中，还是在与Fe2+预孵育后使用，湿润单层都会对酶活性产生显著抑制。这些数据表明LTA会引起膜扰动。此外，基于随后细胞脯氨酰羟化酶活性中Fe2+的可用性，LTA与干燥和湿润单层膜的结合似乎明显不同。LTA作为阳离子交换剂的能力以及LTA无法接触到的细胞内Fe2+的存在，可能解释了在湿润细胞系统中这种两亲分子对脯氨酰羟化酶活性缺乏完全抑制的原因。与在等效干燥制剂中恢复该两亲分子增加的酶活性所需的铁相比，在活细胞中抵消LTA对脯氨酰羟化酶活性的部分抑制所需的铁要少得多。这些以及其他结果表明，虽然LTA不会影响湿润单层中胶原多肽链的形成，但其在分子水平上的参与确实会通过LTA与Fe2+的相互作用导致胶原肽基脯氨酰残基的羟化显著减少。脯氨酰羟化酶活性的这种降低与早期报道的LTA导致成纤维细胞单层中胶原蛋白质羟化的降低相当（O. Leon和C. Panos，《感染与免疫》40:785 - 794，1983）。因此，这些数据表明脯氨酰羟化酶活性的部分抑制与暴露于微量A组12型链球菌LTA的湿润成纤维细胞单层合成有缺陷的胶原直接相关。LTA的使用还表明，这些单层持续形成和积累有缺陷的胶原蛋白质并不需要完全抑制羟脯氨酸的形成。
