LENS PROTEIN ALPHA-CRYSTALLIN B CHAIN

α - b -晶状体蛋白是脊椎动物晶状体的主要成分

Alpha-B-crystallin, a major element of the vertebrate lens, is also expressed in extralenticular tissues. Recent findings indicate that alpha- B-crystallin should be considered a "heat shock" or "stress" protein. First, the alpha-crystallins share homologous sequences with the family of low MW heat shock proteins (hsps). Second, although alpha-B-crystallin is constitutively expressed in some tissues, it can be upregulated dramatically by a variety of classical "stress agents, including heat shock, oxidative stress, and transitional metals. A singular example of alpha-B-crystallin expression occurs in the childhood leukodystrophy, Alexander disease, in which astrocytes accumulate large, proteinaceous inclusions known as Rosenthal fibers. The major components of these inclusions are alpha-B-crystallin and the related small MW heat shock protein, hsp27. Over the first two years of this grant we have found that a). levels of mRNA and protein for alpha-B-crystallin and hsp 27 are markedly elevated in Alexander disease CNS, b). astrocytes upregulate these two genes both coordinately and independently in response to a variety of "stress" agents, and c). alpha-B-crystallin protects astroglial cells from the stress of increased salt concentration. We propose to continue our studies on Alexander disease and to focus on the regulation of small MW heat shock proteins in the central nervous system and shall follow several lines of inquiry: I. Are other hsps overexpressed In Alexander disease and if so, are they involved in RP formation? II. Does the stress-induced increase in alpha-B-crystallin and hsp27 in astrocytes occur at a transcriptional level? III. Can we identify proteins that act as transcriptional regulators for alpha-B-crystallin and hsp27? Do these proteins function in stress responses? Are these proteins expressed in Alexander disease and might they play a role in the accumulation of stress proteins in the Alexander CNS? IV. Does alpha-B-crystallin protect cells from specific "stresses" or does it have general protective properties against many "stresses"?