STRUCTURAL AND FUNCTIONAL STUDIES OF LEDGF

晶状体是一个不同寻常的器官，包含三种不同的细胞类型。一种类型不分裂，但终生存活(中央上皮细胞)，另一种由分裂细胞(有丝分裂带中的上皮细胞)组成，第三种由去核的纤维细胞组成。中央晶状体上皮细胞(LECs)的存活可能需要LECs或其他细胞因子的持续信号传递。虽然大多数脊椎动物细胞在发育过程中需要生长因子来生长和增殖，但对成熟的中央晶状体上皮细胞的存活知之甚少。一种新的生长和存活因子是从具有自身抗体的人晶状体上皮细胞cDNA文库中分离出来的，命名为晶状体上皮衍生生长因子(LEDGF)。LEDGF作为一种生长因子，对晶状体上皮细胞、皮肤成纤维细胞和角质形成细胞具有自分泌和旁分泌作用。它由细胞分泌，结合到细胞表面，定位于细胞核，并调节蛋白质的合成。LEDGF是抵抗热应激、血清饥饿应激和氧化应激的各种细胞类型的生存因子，因为上述细胞没有LEDGF就不能生存。抵抗这些压力的细胞存活的一个基本机制可能是热休克蛋白(HSPs)27和α-晶体蛋白的表达增加。人血清中普遍存在ABS对LEDGF的干扰，通过自身抗体中和LEDGF可阻止细胞生长，最终导致细胞死亡。我们推测，自体抗体耗尽LEDGF后上皮细胞和成纤维细胞的死亡可能是老年性白内障的一个危险因素。这项研究方案包括五个目标。1)进一步确立LEDGF作为多种细胞类型的生长和生存因子。2)确定LEDGF中的重要功能部位。3)分离LEDGF受体并测定其氨基酸序列。4)研究LEDGF及其受体基因的表达与调控。5)探讨LECs在LEDGF存在下存活和LECs死亡的机制。研究LEDGF在晶状体上皮细胞存活和死亡中的基础作用可以提高我们对包括发育、生长和老年性白内障在内的衰老的认识。

The lens is an unusual organ, containing three different cell types. One types does not divide but survives throughout life (central epithelial cells) another consists of dividing cells (epithelial cells in the mitotic zone), & the third is made up of enucleated fiber cells. Survival of central lens epithelial cells (LECs) may require continuous signaling by factors from LECs or other cells. Although most vertebrate cells require growth factors for their growth and proliferation during development, little is known about survival of mature central LECs A novel growth and survival factor was isolated from a human lens epithelial cell cDNA library with auto-antibodies (auto-Abs) cytocidal for LECs and named it lens epithelium-derived growth factor (LEDGF). As a growth factor LEDGF has both autocrine and paracrine effects on LECs, skin fibroblasts, and keratinocytes. It is secreted by the cell, binds to the cell surface, localizes in the nucleus, & regulates protein synthesis. LEDGF is a survival factor for the various cell types against heat- stress, serum starvation-stress, and oxidative-stress, in that the aforementioned cells do not survive without LEDGF. A basic mechanism of cellular survival against these stresses may be an elevated expression of the heat shock proteins (Hsps) 27 and alphaB-crystallin. Abs to LEDGF are prevalent in human sera, and neutralization of LEDGF by auto-Abs blocks cell growth and eventually leads to cell death. We speculate that death of epithelial cells and fibroblasts following the depletion of LEDGF by auto- Abs may be a risk factor for age-related cataract.. This research proposal comprises five aims. 1) To further establish LEDGF as a growth and survival factor for variety of cell types. 2) To determine functionally important sites in LEDGF. 3) To isolate the receptor of LEDGF and determine amino acid sequence. 4) To study expression and regulation of LEDGF and its receptor genes. 5) To investigate the mechanisms of survival of LECs in the presence LEDGF and of death of LECs in its absence. Studying the basic role of LEDGF in survival and death of LECs can enhance our standing of aging including development, growth, and age- related cataract.