Dubaquié Y, Mortensen D L, Intintoli A, Hogue D A, Nakamura G, Rancatore P, Lester P, Sadick M D, Filvaroff E, Fielder P J, Lowman H B
Departments of Protein Engineering Genentech, Inc., South San Francisco, California 94080, USA.
Endocrinology. 2001 Jan;142(1):165-73. doi: 10.1210/endo.142.1.7864.
Insulin-like growth factor I (IGF-I) is a potent anabolic peptide that mediates most of its pleiotropic effects through association with the IGF type I receptor. Biological availability and plasma half-life of IGF-I are modulated by soluble binding proteins (IGFBPs), which sequester free IGF-I into high affinity complexes. Elevated levels of specific IGFBPs have been observed in several pathological conditions, resulting in inhibition of IGF-I activity. Administration of IGF-I variants that are unable to bind to the up-regulated IGFBP species could potentially counteract this effect. We engineered two IGFBP-selective variants that demonstrated 700- and 80,000-fold apparent reductions in affinity for IGFBP-1 while preserving low nanomolar affinity for IGFBP-3, the major carrier of IGF-I in plasma. Both variants displayed wild-type-like potency in cellular receptor kinase assays, stimulated human cartilage matrix synthesis, and retained their ability to associate with the acid-labile subunit in complex with IGFBP-3. Furthermore, pharmacokinetic parameters and tissue distribution of the IGF-I variants in rats differed from those of wild-type IGF-I as a function of their IGFBP affinities. These IGF-I variants may potentially be useful for treating disease conditions associated with up-regulated IGFBP-1 levels, such as chronic or acute renal and hepatic failure or uncontrolled diabetes. More generally, these results suggest that the complex biology of IGF-I may be clarified through in vivo studies of IGFBP-selective variants.
胰岛素样生长因子I（IGF-I）是一种强效的合成代谢肽，它通过与I型胰岛素样生长因子受体结合来介导其大部分多效性作用。IGF-I的生物利用度和血浆半衰期受可溶性结合蛋白（IGFBPs）调节，这些蛋白将游离的IGF-I隔离成高亲和力复合物。在几种病理状态下已观察到特定IGFBPs水平升高，导致IGF-I活性受到抑制。给予无法与上调的IGFBP种类结合的IGF-I变体可能会抵消这种作用。我们构建了两种IGFBP选择性变体，它们对IGFBP-1的亲和力明显降低了700倍和80,000倍，同时对血浆中IGF-I的主要载体IGFBP-3保持低纳摩尔亲和力。在细胞受体激酶试验中，这两种变体均表现出类似野生型的效力，刺激了人类软骨基质合成，并保留了与IGFBP-3复合物中的酸不稳定亚基结合的能力。此外，大鼠体内IGF-I变体的药代动力学参数和组织分布因其对IGFBP的亲和力不同而与野生型IGF-I有所差异。这些IGF-I变体可能对治疗与IGFBP-1水平上调相关的疾病状态有用，如慢性或急性肾、肝功能衰竭或未控制的糖尿病。更普遍地说，这些结果表明，通过对IGFBP选择性变体的体内研究可能会阐明IGF-I复杂生物学特性。
