CORRECT PROTEOLYTIC CLEAVAGE IS REQUIRED FOR THE CELL ADHESIVE FUNCTION OF UVOMORULIN
CORRECT PROTEOLYTIC CLEAVAGE IS REQUIRED FOR THE CELL ADHESIVE FUNCTION OF UVOMORULIN
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DOI：
10.1083/jcb.111.4.1645
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发表时间：
1990-10-01
影响因子：
7.8
通讯作者：
KEMLER, R
中科院分区：
文献类型：
--
作者：
OZAWA, M;KEMLER, R
所有的Ca 2+依赖性细胞粘附分子都是作为前体多肽合成的，随后进行一系列翻译后修饰，包括蛋白水解切割。成熟蛋白质在细胞内形成并运输到细胞表面。对于uvomorulin，前体片段由129个氨基酸残基组成，其被切割以产生120-kD成熟蛋白。为了阐明蛋白水解加工的作用，我们构建了编码突变体uvomorulin的cDNA，该突变体uvomorulin不能再被内源性蛋白水解酶加工，并在L细胞中表达突变体多肽。而不是内源性蛋白酶的识别位点，这些突变体含有血清凝血因子Xa的识别位点或新的胰蛋白酶切割位点。在这两种情况下，突变多肽的细胞内蛋白水解加工被抑制。未加工的多肽有效地表达在细胞表面上，并具有其他功能的共同与成熟的uvomorulin，如复合物的形成与连环蛋白和Ca 2+依赖性的抗蛋白水解降解。然而，表达未加工的多肽的细胞没有表现出uvomrulin介导的粘附功能。用相应的蛋白酶处理突变蛋白质导致前体区域的切割和uvomorulin功能的激活。然而，其他蛋白酶虽然去除了前体片段，但在激活粘合功能方面无效。这些结果表明，正确的加工是必需的，为uvomorulin功能，并强调的重要性，成熟uvomorulin多肽的氨基末端区域的粘附的分子机制。
All Ca2+-dependent cell adhesion molecules are synthesized as precursor polypeptides followed by a series of posttranslational modifications including proteolytic cleavage. The mature proteins are formed intracellularly and transported to the cell surface. For uvomorulin the precursor segment is composed of 129-amino acid residues which are cleaved off to generate the 120-kD mature protein. To eluclidate the role of proteolytic processing, we constructed cDNAs encoding mutant uvomorulin that could no longer be processed by endogenous proteolytic enzymes and expressed the mutant polypeptides in L cells. Instead of the recognition sites for endogenous proteases, these mutants contained either a recognition site of serum coagulation factor Xa or a new trypsin cleavage site. The intracellular proteolytic processing of mutant polypeptides was inhibited in both cases. The unprocessed polypeptides were efficiently expressed on the cell surface and had other features in common with mature uvomorulin, such as complex formation with catenins and Ca2+-dependent resistance to proteolytic degradation. However, cells expressing unprocessed polypeptides showed no uvomrulinmediated adhesive function. Treatment of the mutant proteins with the respective proteases results in cleavage of the precursor region and the activation of uvomorulin function. However, other proteases although removing the precursor segment were ineffective in activating the adhesive function. These results indicate that correct processing is required for uvomorulin function and emphasize the importance of the amino-terminal region of mature uvomorulin polypeptide in the molecular mechanism of adhesion.