Cyclic peptides from the loop region of the laminin alpha 4 chain LG4 module show enhanced biological activity over linear peptides.
Cyclic peptides from the loop region of the laminin alpha 4 chain LG4 module show enhanced biological activity over linear peptides.
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DOI：
10.1021/bi049009u
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发表时间：
2004-10
期刊：
影响因子：
2.9
通讯作者：
F. Yokoyama;N. Suzuki;M. Haruki;N. Nishi;S. Oishi;N. Fujii;A. Utani;H. Kleinman;M. Nomizu
中科院分区：
文献类型：
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作者：
F. Yokoyama;N. Suzuki;M. Haruki;N. Nishi;S. Oishi;N. Fujii;A. Utani;H. Kleinman;M. Nomizu
层粘连蛋白是基底膜上的异源三聚体糖蛋白，参与多种生物活性。到目前为止，已经鉴定了5条α链、3条β链和3条伽马链，并且至少存在15种由不同的三条链的不同组合组成的层粘连蛋白亚型。层粘连蛋白的主要细胞表面受体是整合素和蛋白多糖，如营养不良多聚糖和突触多聚糖。此前，我们报道了合成肽A4G82(TLFLAHGRLVFM，鼠层粘连蛋白α4链残基1514-1525)具有很强的细胞黏附和Syndecan结合活性。根据LG模块的晶体结构和序列比对，A4G82位于层粘连蛋白α4链LG4模块中β链E和F之间的连接环区。在这里，我们重点研究了这个E-F环区对α4链LG4模块生物活性的结构重要性。为了确定环结构的重要性，我们合成了A4G82X(环-A4G82X，Cys-TLFLAHGRLVFX-Cys，X=去亮氨酸)，它是通过N-端和C-端的二硫键环化的。A4G82X环肽抑制α4链G结构域的肝素结合活性，促进HT-1080细胞黏附能力强于相应的线状多肽。我们使用一系列截短肽确定FLAHGRLVFX是对细胞黏附和肝素结合重要的环-A4G82X的最小序列。此外，肝素能更有效地阻断HT-1080细胞与环肽的黏附，而不是细胞黏附于线状肽。此外，环肽还显著增强了Syndecan-2介导的细胞黏附活性。这些结果表明，A4G82的活性是高度构象依赖的，表明E-F环结构对其生物活性至关重要。
Laminins, heterotrimeric glycoproteins in the basement membrane, are involved in diverse biological activities. So far, five alpha, three beta, and three gamma chains have been identified, and at least 15 laminin isoforms exist composed of various combinations of the different three chains. The major cell-surface receptors for laminins are integrins and proteoglycans, such as dystroglycans and syndecans. Previously, we reported that synthetic peptide A4G82 (TLFLAHGRLVFM, mouse laminin alpha4 chain residues 1514-1525) showed strong cell attachment and syndecan binding activities. On the basis of the crystal structure of the LG module and sequence alignment, A4G82 is located in the connecting loop region between beta-strands E and F in the laminin alpha4 chain LG4 module. Here, we have focused on the structural importance of this E-F loop region for the biological activity of the alpha4 chain LG4 module. To determine the importance of the loop structure, we synthesized peptide A4G82X (cyclo-A4G82X, Cys-TLFLAHGRLVFX-Cys, X= norleucine), which was cyclized via disulfide bridges at both the N- and C-termini. The cyclic peptides derived from A4G82X inhibited the heparin binding activity of the alpha4 chain G domain and promoted HT-1080 cell attachment better than the corresponding linear peptides. We determined FLAHGRLVFX as a minimal sequence of cyclo-A4G82X important for cell adhesion and heparin binding using a series of truncated peptides. Moreover, HT-1080 cell attachment to the cyclic peptides was more efficiently blocked by heparin than cell attachment to the linear peptides. Furthermore, the cyclic peptides showed significantly enhanced syndecan-2-mediated cell attachment activity. These results indicate that the activity of A4G82 is highly conformation-dependent, suggesting that the E-F loop structure is crucial for its biological activity.