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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Embryos of the brine shrimp, Artemia franciscana, exhibit remarkable resistance to physiological stress, which is temporally correlated with the presence of two proteins, one a small heat shock/alpha-crystallin protein termed p26 and the other called artemin, of unknown function. Artemin was sequenced previously by Edman degradation, and its relationship to ferritin, an iron storage protein, established. The isolation from an Artemia expressed sequence tag library of artemin and ferritin cDNAs extends this work. Artemin cDNA was found to contain an ORF of 693 nucleotides, and its deduced amino-acid sequence, except for the initiator methionine, was identical with that determined previously. Ferritin cDNA is 725 bp in length with an ORF of 516 nucleotides. Artemin amino-acid residues 32-185 are most similar to ferritin, but artemin is enriched in cysteines. The abundance of cysteines and their intramolecular spatial distribution suggest that artemin protects embryos against oxidative damage and/or that its function is redox regulated. The conserved regions in artemin and ferritin monomers are structurally similar to one another and both proteins assemble into oligomers. However, modeling of the quaternary structure indicated that artemin multimers lack the central space used for metal storage that characterizes ferritin oligomers, implying different roles for this protein. Probing of Northern blots revealed two artemin transcripts, one of 3.5 kb and another of 2.2 kb. These transcripts decreased in parallel and had almost disappeared by 16 h of development. The ferritin transcript of 0.8 kb increased slightly during reinitiation of development, then declined, and was almost completely gone by 16 h. Clearly, the loss of artemin and ferritin during embryo development is due to transcriptional regulation and proteolytic degradation of the proteins.
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PMID:Molecular characterization of artemin and ferritin from Artemia franciscana. 1249 84

Embryos of the brine shrimp, Artemia franciscana, either develop directly into swimming larvae or are released from females as encysted gastrulae (cysts) which enter diapause, a reversible state of dormancy. Metabolic activity in diapause cysts is very low and these embryos are remarkably resistant to physiological stresses. Encysting embryos, but not those undergoing uninterrupted development, synthesize large amounts of two proteins, namely p26 and artemin. Cloning and sequencing demonstrated p26 is a small heat shock/alpha-crystallin protein while artemin has structural similarity to ferritin. p26 exhibits molecular chaperone activity in vitro, moves reversibly into nuclei during stress and confers thermotolerance on transformed organisms, suggesting critical roles in cyst development. The function of artemin is unknown. Encysted Artemia also contain an abundance of trehalose, a disaccharide capable of protecting embryos. Artemia represent a novel experimental system where the developmental functions of small heat shock/alpha-crystallin proteins and other stress response elements can be explored.
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PMID:Molecular chaperones, stress resistance and development in Artemia franciscana. 1498 54

Females of the crustacean Artemia franciscana produce either motile nauplii or gastrula stage embryos enclosed in a shell impermeable to nonvolatile compounds and known as cysts. The encysted embryos enter diapause, a state of greatly reduced metabolism and profound stress tolerance. Artemin, a diapause-specific ferritin homolog in cysts has molecular chaperone activity in vitro. Artemin represents 7.2% of soluble protein in cysts, approximately equal to the amount of p26, a small heat shock protein. However, there is almost twice as much artemin mRNA in cysts as compared with p26 mRNA, suggesting that artemin mRNA is translated less efficiently. RNA interference employing the injection of artemin double-stranded RNA into the egg sacs of A. franciscana females substantially reduced artemin mRNA and protein in cysts. Decreasing artemin diminished desiccation and freezing tolerance of cysts, demonstrating a role for this protein in stress resistance. Knockdown of artemin increased the time required for complete discharge of a brood of cysts carried within a female from a few hours up to 4 days, an effect weakened in successive broods. Artemin, an abundant molecular chaperone, contributes to stress tolerance of A. franciscana cysts while influencing their development and/or exit from females.
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PMID:Artemin, a diapause-specific chaperone, contributes to the stress tolerance of Artemia franciscana cysts and influences their release from females. 2452 27

Oviparously developing embryos of the brine shrimp, Artemia, arrest at gastrulation and are released from females as cysts before entering diapause, a state of dormancy and stress tolerance. Diapause is terminated by an external signal, and growth resumes if conditions are permissible. However, if circumstances are unfavorable, cysts enter quiescence, a dormant stage that continues as long as adverse conditions persist. Artemia embryos in diapause and quiescence are remarkably resistant to environmental and physiological stressors, withstanding desiccation, cold, heat, oxidation, ultraviolet radiation, and years of anoxia at ambient temperature when fully hydrated. Cysts have adapted to stress in several ways; they are surrounded by a rigid cell wall impermeable to most chemical compounds and which functions as a shield against ultraviolet radiation. Artemia cysts contain large amounts of trehalose, a non-reducing sugar thought to preserve membranes and proteins during desiccation by replacing water molecules and/or contributing to vitrification. Late embryogenesis abundant proteins similar to those in seeds and other anhydrobiotic organisms are found in cysts, and they safeguard cell organelles and proteins during desiccation. Artemia cysts contain abundant amounts of p26, a small heat shock protein, and artemin, a ferritin homologue, both ATP-independent molecular chaperones important in stress tolerance. The evidence provided in this review supports the conclusion that it is the interplay of these protective elements that make Artemia one of the most stress tolerant of all metazoan organisms.
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PMID:Stress tolerance during diapause and quiescence of the brine shrimp, Artemia. 2633 84

Embryos of the crustacean, Artemia franciscana, may undergo oviparous development, forming encysted embryos (cysts) that are released from females and enter diapause, a state of suppressed metabolism and greatly enhanced stress tolerance. Diapause-destined embryos of A. franciscana synthesize three small heat shock proteins (sHsps), p26, ArHsp21 and ArHsp22, as well as artemin, a ferritin homologue, all lacking in embryos that develop directly into nauplii. Of these diapause-specific molecular chaperones, p26 and artemin are important contributors to the extraordinary stress tolerance of A. franciscana cysts, but how their synthesis is regulated is unknown. To address this issue, a cDNA for heat shock factor 1 (Hsf1), shown to encode a protein similar to Hsf1 from other organisms, was cloned from A. franciscana. Hsf1 was knocked down by RNA interference (RNAi) in nauplii and cysts of A. franciscana. Nauplii lacking Hsf1 died prematurely upon release from females, showing that this transcription factor is essential to the survival of nauplii. Diapause cysts with diminished amounts of Hsf1 were significantly less stress tolerant than cysts containing normal levels of Hsf1. Moreover, cysts deficient in Hsf1 possessed reduced amounts of p26, ArHsp21, ArHsp22 and artemin, revealing dependence on Hsf1 for expression of their genes and maximum stress tolerance. The results demonstrate an important role for Hsf1, likely in concert with other transcription factors, in the survival and growth of A. franciscana and in the developmentally regulated synthesis of proteins responsible for the stress tolerance of diapausing A. franciscana cysts.
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PMID:Stress tolerance in diapausing embryos of Artemia franciscana is dependent on heat shock factor 1 (Hsf1). 2997 76

The crustacean, Artemia franciscana, displays a complex life history in which embryos either arrest development and undertake diapause as cysts or they develop into swimming nauplii. Diapause entry is preceded during embryogenesis by the synthesis of specific molecular chaperones, namely the small heat shock proteins p26, ArHsp21, and ArHsp22, and the ferritin homolog, artemin. Maximal synthesis of diapause-specific molecular chaperones is dependent on the transcription factor, heat shock factor 1 (Hsf1), found in similar amounts in cysts and nauplii newly released from females. This investigation was performed to determine why, if cysts and nauplii contain comparable amounts of Hsf1, only cyst-destined embryos synthesize diapause-specific molecular chaperones. Quantification by qPCR and immunoprobing of Western blots, respectively, demonstrated that hsf1 mRNA and Hsf1 peaked by day 2 post-fertilization in embryos that were developing into cysts and then declined. hsf1 mRNA and Hsf1 were present in nauplii-destined embryos on day 2 post-fertilization, but in much smaller amounts than in cyst-destined embryos, and they increased in quantity until release of nauplii from females. Immunofluorescent staining revealed that the amount of Hsf1 in nuclei was greatest on day 4 post-fertilization in cyst-destined embryos but could not be detected in nuclei of nauplius-destined embryos at this time. The differences in quantity and location of Hsf1 explain why embryos fated to become cysts and eventually enter diapause synthesize p26, ArHsp21, ArHsp22, and artemin, whereas nauplius-destined embryos do not produce these molecular chaperones.
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PMID:The synthesis of diapause-specific molecular chaperones in embryos of Artemia franciscana is determined by the quantity and location of heat shock factor 1 (Hsf1). 3070 77