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Mu-crystallin is a mammalian homologue of Agrobacterium ornithine cyclodeaminase and is expressed in human retina.

ABSTRACT: mu-Crystallin is the major component of the eye lens in several Australian marsupials. The complete sequence of kangaroo mu-crystallin has now been obtained by cDNA cloning. The predicted amino acid sequence shows similarity with ornithine cyclodeaminases encoded by the tumor-inducing (Ti) plasmids of Agrobacterium tumefaciens. Until now, neither ornithine cyclodeaminase nor any structurally related enzymes have been observed in eukaryotes. RNA analysis of kangaroo tissues shows that mu-crystallin is expressed at high abundance in lens, but outside the lens mu-crystallin is preferentially expressed in neural tissues, retina, and brain. An almost full-length cDNA for mu-crystallin was cloned from human retina. In human tissues, mu-crystallin mRNA is present in neural tissue, muscle, and kidney. This pattern of expression and relationship to an enzyme involved in unusual amino acid metabolism suggests the interesting possibility that mammalian mu-crystallins could be enzymes participating in processes such as osmoregulation or the metabolism of excitatory amino acids.

SUBMITTER: Kim RY

PROVIDER: S-EPMC50112 | biostudies-other | 1992 Oct

REPOSITORIES: biostudies-other

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mu-crystallin is a mammalian homologue of Agrobacterium ornithine cyclodeaminase and is expressed in human retina.

Kim R Y RY Gasser R R Wistow G J GJ

Proceedings of the National Academy of Sciences of the United States of America 19921001 19

mu-Crystallin is the major component of the eye lens in several Australian marsupials. The complete sequence of kangaroo mu-crystallin has now been obtained by cDNA cloning. The predicted amino acid sequence shows similarity with ornithine cyclodeaminases encoded by the tumor-inducing (Ti) plasmids of Agrobacterium tumefaciens. Until now, neither ornithine cyclodeaminase nor any structurally related enzymes have been observed in eukaryotes. RNA analysis of kangaroo tissues shows that mu-crystall ...[more]

PMID: 1384048

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Project description:Misfolded protein aggregation, including cataract, cause a significant amount of blindness worldwide. ?-Crystallin is reported to bind misfolded proteins and prevent their aggregation. We hypothesize that supplementing retina and lens with ?-crystallin may help to delay disease onset. The purpose of this study was to determine if ?B-crystallin subunits containing a cell penetration peptide (gC-tagged ?B-crystallin) facilitate the uptake of wild type ?A-crystallin (WT-?A) in lens and retina. Recombinant human ?B-crystallin was modified by the addition of a novel cell penetration peptide derived from the gC gene product of herpes simplex virus (gC-?B). Recombinant gC-?B and wild-type ?A-crystallin (WT-?A) were purified from E. coli over-expression cultures. After Alexa-labeling of WT-?A, these proteins were mixed at ratios of 1:2, 1:5 and 1:10, respectively, and incubated at 37°C for 4 hours to allow for subunit exchange. Mixed oligomers were subsequently incubated with tissue culture cells or mouse organ cultures. Similarly, crystallin mixtures were injected into the vitreous of rat eyes. At various times after exposure, tissues were harvested and analyzed for protein uptake by confocal microscopy or flow cytometry. Chaperone-like activity assays were performed on ?-crystallins ratios showing optimal uptake using chemically-induced or heat induced substrate aggregation assays. As determined by flow cytometry, a ratio of 1:5 for gC-?B to WT-?A was found to be optimal for uptake into retinal pigmented epithelial cells (ARPE-19). Chaperone-like activity assays demonstrated that hetero-oligomeric complex of gC-?B to WT-?A (in 1:5 ratio) retained protein aggregation protection. We observed a significant increase in protein uptake when optimized (gC-?B to WT-?A (1:5 ratio)) hetero-oligomers were used in mouse lens and retinal organ cultures. Increased levels of ?-crystallin were found in lens and retina following intravitreal injection of homo- and hetero-oligomers in rats.

Dataset Information

Mu-crystallin is a mammalian homologue of Agrobacterium ornithine cyclodeaminase and is expressed in human retina.

Publications

mu-crystallin is a mammalian homologue of Agrobacterium ornithine cyclodeaminase and is expressed in human retina.

Similar Datasets

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