LTBP-2 specifically interacts with the amino-terminal region of fibrillin-1 and competes with LTBP-1 for binding to this microfibrillar protein
LTBP-2 specifically interacts with the amino-terminal region of fibrillin-1 and competes with LTBP-1 for binding to this microfibrillar protein
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DOI：
10.1016/j.matbio.2006.12.006
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发表时间：
2007-05-01
期刊：
影响因子：
6.9
通讯作者：
Gibson, Mark A.
中科院分区：
文献类型：
--
作者：
Hirani, Rena;Hanssen, Eric;Gibson, Mark A.
LTBP-2是一种功能未知的基质蛋白，因为与其他ltbp不同，它不与潜在的tgf - β形成共价复合物。我们之前已经证明LTBP-2与发育中的主动脉和其他组织中含有纤维蛋白的微原纤维广泛相关。我们现在已经证明，在固相测定和覆盖印迹中，全长人重组LTBP-2特异性地结合到纤颤蛋白1的氨基末端区域，而不是纤颤蛋白2。在实验缓冲液中加入2 mM Ca2+离子增强了这种结合，并被5 mM EDTA消除，这表明这种相互作用是直接或间接依赖于Ca2+离子的。根据特异结合曲线计算出相互作用的Kd为9.4 nM。LTBP-2的重组羧基末端片段A)结合了纤原蛋白1的氨基末端片段，b)完全阻断了全长LTBP-2与纤原蛋白1的结合。这一结果表明，主要的纤维蛋白1结合位点位于LTBP-2的羧基端附近。进一步的竞争性结合研究表明，LTBP-1类似的羧基端片段能够阻断LTBP-2与纤原蛋白1的结合，而LTBP-2的c端片段能够阻断LTBP-1片段与纤原蛋白的相互作用。因此，LTBP-2在纤颤蛋白-1上的结合位点似乎与LTBP-1相同或非常接近。发育中的人主动脉免疫组织化学分析显示LTBPs-1和-2的分布不同，但广泛重叠。两种ltbp均与纤维蛋白-1和弹性薄片广泛共定位，但LTBP-2在整个内层具有广泛的信号，而LTBP-1仅在外内层具有强烈的定位。这一发现表明，LTBP-2有可能与LTBP-1竞争，以结合整个主动脉壁的含有纤维蛋白的微原纤维，特别是在LTBP-1主要位于的外内侧区域。总的来说，结果支持LTBP-2可能是主动脉和其他富含纤维蛋白组织的微纤维储存大量潜在tgf - β复合物的间接负调节因子的概念。(C) 2007 Elsevier B.V./国际基质生物学学会。版权所有。
LTBP-2 is a matrix protein of unknown function since, unlike other LTBPs, it does not form covalent complexes with latent TGF-beta. We have previously shown that LTBP-2 has widespread association with fibrillin-containing microfibrils in developing aorta and other tissues. We have now shown that full-length human recombinant LTBP-2 specifically binds to the amino-terminal region of fibrillin-1, but not to fibrillin-2, in solid phase assays and overlay blotting. The binding was enhanced by the inclusion of 2 mM Ca2+ ions in the assay buffer and abolished by 5 mM EDTA indicating that the interaction was directly or indirectly Ca2+ ion dependent. The Kd for the interaction was calculated from the specific binding curve as 9.4 nM. A recombinant carboxyl-terminal fragment of LTBP-2 was shown to a) bind the amino-terminal fragment of fibrillin-1 and b) block completely the binding of full length LTBP-2 to fibrillin-1. This result indicates that the major fibrillin-1 binding site resides close to the carboxyl-terminus of LTBP-2. Further competitive binding studies showed that an analogous carboxyl terminal fragment of LTBP-1 was able to block the binding of LTBP-2 to fibrillin-1 and that the C-terminal fragment of LTBP-2 could block the interaction of the LTBP-1 fragment with the fibrillin. Thus the binding site for LTBP-2 on fibrillin-1 appears to be the same or in close proximity to that for LTBP-1. Immunohistochemical analysis of developing human aorta showed distinctive but extensively overlapping distributions for LTBPs-1 and -2. Both LTBPs showed extensive co-localization with fibrillin-1 and elastic lamellae but LTBP-2 had extensive signal throughout the medial layer whereas LTBP-1 showed strong localization only in the outer medial layer. The finding indicates that there is a possibility for LTBP-2 to compete with LTBP-1 for binding to fibrillin-containing microfibrils throughout the aortic wall but particularly in the outer medial region where the LTBP-1 is predominantly located. Overall, the results support the concept that that LTBP-2 may be an indirect negative modulator for storage of the large latent TGF-beta complex on microfibrils in aorta and other fibrillin-rich tissues. (C) 2007 Elsevier B.V./International Society of Matrix Biology. All rights reserved.