Thomas John Terrig, Moos Malcolm
Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Bethesda, MD 20892, USA.
Dev Biol. 2007 Oct 1;310(1):129-39. doi: 10.1016/j.ydbio.2007.07.032. Epub 2007 Aug 2.
Unlike most transforming growth factor-beta (TGF-beta) superfamily members, Vg1 has been shown not to produce gross phenotypic alterations in Xenopus embryos when overexpressed by mRNA injection. Experiments with artificial chimeric constructs and a recently identified second allele of Vg1 suggest that this may be due to unusually stringent requirements for proteolytic processing. We provide biological and biochemical evidence that cleavage by two distinct proteolytic enzymes is required for effective activation of Vg1. We demonstrate a tightly restricted overlap in expression patterns of Vg1 with the proteases required to release the mature peptide. The data presented may account for the long-standing observation that the vast majority of Vg1 protein, in vivo, is present in its unprocessed form. Taken together, these observations provide a plausible mechanism for local action of Vg1 consistent with requirements imposed by current models of pattern formation in the developing body axis.
与大多数转化生长因子-β（TGF-β）超家族成员不同，研究表明，通过mRNA注射过表达时，Vg1在非洲爪蟾胚胎中不会产生明显的表型改变。对人工嵌合构建体和最近鉴定出的Vg1第二个等位基因的实验表明，这可能是由于对蛋白水解加工有异常严格的要求。我们提供了生物学和生化证据，表明Vg1的有效激活需要两种不同的蛋白水解酶进行切割。我们证明Vg1的表达模式与释放成熟肽所需的蛋白酶之间存在紧密受限的重叠。所呈现的数据可能解释了长期以来的观察结果，即在体内，绝大多数Vg1蛋白以未加工的形式存在。综上所述，这些观察结果为Vg1的局部作用提供了一种合理的机制，这与当前发育体轴模式形成模型所提出的要求一致。
