Schulte A, Schulz B, Andrzejewski M G, Hundhausen C, Mletzko S, Achilles J, Reiss K, Paliga K, Weber C, John S Rose, Ludwig A
Institute of Biochemistry, Christian-Albrechts-University, Kiel, Germany.
Biochem Biophys Res Commun. 2007 Jun 22;358(1):233-40. doi: 10.1016/j.bbrc.2007.04.100. Epub 2007 Apr 24.
The chemokines CX3CL1/Fractalkine and CXCL16 are expressed as transmembrane molecules and can mediate cell-cell-adhesion. By proteolytic processing, CX3CL1 and CXCL16 are released from the cell surface by proteolytic shedding resulting in the generation of soluble chemoattractants. This ectodomain release is mediated by the alpha-secretase-like activity of the two disintegrins and metalloproteinases ADAM10 and ADAM17. Using CX3CL1 and CXCL16 constructs C-terminally fused to two Z-domains of Protein A (2Z-tag) we detect C-terminal fragments (CTFs) of both chemokines resulting from ADAM10-mediated cleavages at multiple sites as examined by inhibitor studies. Furthermore, inhibitor studies as well as genetic studies using presenilin 1/2-deficient cell lines suggest the involvement of gamma-secretase-but not beta-secretase-like activity in the processing of transmembrane chemokines. The combination of alpha- and gamma-secretase and proteasomal inhibitors points towards a sequential processing of transmembrane chemokines by first ADAM10 and then gamma-secretases and possible further degradation. This proteolytic processing cascade of transmembrane chemokines is similar to that described for Notch and E-cadherin where CTFs generated by gamma-secretase serve as intracellular signal transmitters.
趋化因子CX3CL1/ fractalkine和CXCL16作为跨膜分子表达，并可介导细胞间粘附。通过蛋白水解过程，CX3CL1和CXCL16通过蛋白水解脱落从细胞表面释放，从而产生可溶性趋化因子。这种胞外域释放由两种解整合素和金属蛋白酶ADAM10和ADAM17的α-分泌酶样活性介导。使用C末端与蛋白A的两个Z结构域（2Z标签）融合的CX3CL1和CXCL16构建体，我们检测到两种趋化因子的C末端片段（CTF），这些片段是由ADAM10介导的多个位点切割产生的，如抑制剂研究所示。此外，抑制剂研究以及使用早老素1/2缺陷细胞系的遗传学研究表明，γ-分泌酶而非β-分泌酶样活性参与跨膜趋化因子的加工过程。α-分泌酶、γ-分泌酶和蛋白酶体抑制剂的联合作用表明，跨膜趋化因子首先由ADAM10进行加工，然后由γ-分泌酶进行加工，并可能进一步降解。这种跨膜趋化因子的蛋白水解加工级联与Notch和E-钙粘蛋白的情况类似，其中γ-分泌酶产生的CTF作为细胞内信号传递分子。
