scholarly journals The molecular chaperone Hsp90α deficiency causes retinal degeneration by disrupting Golgi organization and vesicle transportation in photoreceptors

2019 ◽  
Vol 12 (3) ◽  
pp. 216-229 ◽  
Author(s):  
Yuan Wu ◽  
Xiudan Zheng ◽  
Yubo Ding ◽  
Min Zhou ◽  
Zhuang Wei ◽  
...  
Keyword(s):  
Retinal Degeneration ◽  
Molecular Chaperone ◽  
Outer Segment ◽  
Microscopic Analysis ◽  
Heat Shock Protein 90 ◽  
Hsp90 Inhibitor ◽  
Wild Type ◽  
Electron Microscopic ◽  
Golgi Organization ◽  
Deficient Mice

Abstract Heat shock protein 90 (Hsp90) is an abundant molecular chaperone with two isoforms, Hsp90α and Hsp90β. Hsp90β deficiency causes embryonic lethality, whereas Hsp90α deficiency causes few abnormities except male sterility. In this paper, we reported that Hsp90α was exclusively expressed in the retina, testis, and brain. Its deficiency caused retinitis pigmentosa (RP), a disease leading to blindness. In Hsp90α-deficient mice, the retina was deteriorated and the outer segment of photoreceptor was deformed. Immunofluorescence staining and electron microscopic analysis revealed disintegrated Golgi and aberrant intersegmental vesicle transportation in Hsp90α-deficient photoreceptors. Proteomic analysis identified microtubule-associated protein 1B (MAP1B) as an Hsp90α-associated protein in photoreceptors. Hspα deficiency increased degradation of MAP1B by inducing its ubiquitination, causing α-tubulin deacetylation and microtubule destabilization. Furthermore, the treatment of wild-type mice with 17-DMAG, an Hsp90 inhibitor of geldanamycin derivative, induced the same retinal degeneration as Hsp90α deficiency. Taken together, the microtubule destabilization could be the underlying reason for Hsp90α deficiency-induced RP.

scholarly journals Ifm(2)2 is a myosin heavy chain allele that disrupts myofibrillar assembly only in the indirect flight muscle of Drosophila melanogaster.

1988 ◽  
Vol 107 (6) ◽  
pp. 2613-2621 ◽  
Author(s):  
M Chun ◽  
S Falkenthal
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Flight Muscle ◽  
Microscopic Analysis ◽  
Thick Filament ◽  
Indirect Flight Muscle ◽  
Chain Gene ◽  
Wild Type ◽  
Electron Microscopic ◽  
Sarcomere Assembly

Using a combination of molecular and genetic techniques we demonstrate that Ifm(2)2 is an allele of the single-copy sarcomeric myosin heavy chain gene. Flies homozygous for this allele accumulate wild-type levels of mRNA and protein in tubular muscle of adults, but fail to accumulate detectable amounts of myosin heavy chain mRNA or protein in the indirect flight muscle. We propose that the mutation interferes with either transcription of the gene or splicing of the primary transcript in the indirect flight muscle and not in other muscle tissues. Biochemical and electron microscopic analysis of flies homozygous for this mutation has revealed that thick filament assembly is abolished in the indirect flight muscle resulting in the instability of wild-type thick filament proteins. In contrast, thin filament and Z disc assembly are marginally affected. We discuss a working hypothesis for sarcomere assembly and define and experimental approach to test the predictions of this proposed pathway for sarcomere assembly.

Syk expression in endothelial cells and their morphologic defects in embryonic Syk-deficient mice

Blood ◽  
2001 ◽  
Vol 98 (9) ◽  
pp. 2869-2871 ◽  
Author(s):  
Shigeru Yanagi ◽  
Ryoko Inatome ◽  
Junyi Ding ◽  
Hironori Kitaguchi ◽  
Victor L. J. Tybulewicz ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Cell Function ◽  
Critical Role ◽  
Microscopic Analysis ◽  
Electron Microscopic ◽  
Vascular Integrity ◽  
Endothelial Cell Function ◽  
Deficient Mice

Abstract Mice deficient in the Syk tyrosine kinase showed severe petechiae in utero and died shortly after birth. The mechanism of this bleeding, however, remains unknown. Here it is shown that this bleeding is caused by morphologic defects of Syk-deficient endothelial cells during embryogenesis. Immunoblot and reverse transcriptase–polymerase chain reaction Northern blot analysis indicated that Syk is expressed in several endothelial cell lines. Immunocytochemical analysis also confirmed that Syk is expressed in the normal embryonic endothelial cells and is absent in Syk-deficient mice. Furthermore, electron microscopic analysis of Syk-deficient mice revealed an abnormal morphogenesis and a decreased number of endothelial cells. The results indicate a critical role for Syk in endothelial cell function and in maintaining vascular integrity in vivo.

scholarly journals Gambogic acid identifies an isoform-specific druggable pocket in the middle domain of Hsp90β

2016 ◽  
Vol 113 (33) ◽  
pp. E4801-E4809 ◽  
Author(s):  
Kendrick H. Yim ◽  
Thomas L. Prince ◽  
Shiwei Qu ◽  
Fang Bai ◽  
Patricia A. Jennings ◽  
...  
Keyword(s):  
Molecular Chaperone ◽  
Drug Targets ◽  
Heat Shock Protein 90 ◽  
Hsp90 Inhibitor ◽  
Gambogic Acid ◽  
Disease States ◽  
Middle Domain ◽  
Health And Disease ◽  
A Site

Because of their importance in maintaining protein homeostasis, molecular chaperones, including heat-shock protein 90 (Hsp90), represent attractive drug targets. Although a number of Hsp90 inhibitors are in preclinical/clinical development, none strongly differentiate between constitutively expressed Hsp90β and stress-induced Hsp90α, the two cytosolic paralogs of this molecular chaperone. Thus, the importance of inhibiting one or the other paralog in different disease states remains unknown. We show that the natural product, gambogic acid (GBA), binds selectively to a site in the middle domain of Hsp90β, identifying GBA as an Hsp90β-specific Hsp90 inhibitor. Furthermore, using computational and medicinal chemistry, we identified a GBA analog, referred to as DAP-19, which binds potently and selectively to Hsp90β. Because of its unprecedented selectivity for Hsp90β among all Hsp90 paralogs, GBA thus provides a new chemical tool to study the unique biological role of this abundantly expressed molecular chaperone in health and disease.

scholarly journals The sep1 mutant of Saccharomyces cerevisiae arrests in pachytene and is deficient in meiotic recombination.

Genetics ◽  
1995 ◽  
Vol 139 (2) ◽  
pp. 495-509 ◽  
Author(s):  
D X Tishkoff ◽  
B Rockmill ◽  
G S Roeder ◽  
R D Kolodner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Recombination ◽  
Microscopic Analysis ◽  
Mutant Gene ◽  
Strand Break ◽  
Strand Exchange ◽  
Wild Type ◽  
Electron Microscopic ◽  
Pathways Analysis

Abstract Strand exchange protein 1 (Sep1) from Saccharomyces cerevisiae promotes homologous pairing of DNA in vitro and sep1 mutants display pleiotropic phenotypes in both vegetative and meiotic cells. In this study, we examined in detail the ability of the sep1 mutant to progress through meiosis I prophase and to undergo meiotic recombination. In meiotic return-to-growth experiments, commitment to meiotic recombination began at the same time in wild type and mutant; however, recombinants accumulated at decreased rates in the mutant. Gene conversion eventually reached nearly wild-type levels, whereas crossing over reached 15-50% of wild type. In an assay of intrachromosomal pop-out recombination, the sep1, dmc1 and rad51 single mutations had only small effects; however, pop-out recombination was virtually eliminated in the sep1 dmc1 and sep1 rad51 double mutants, providing evidence for multiple recombination pathways. Analysis of meiotic recombination intermediates indicates that the sep1 mutant is deficient in meiotic double-strand break repair. In a physical assay, the formation of mature reciprocal recombinants in the sep1 mutant was delayed relative to wild type and ultimately reached only 50% of the wild-type level. Electron microscopic analysis of meiotic nuclear spreads indicates that the sep1 delta mutant arrests in pachytene, with apparently normal synaptonemal complex. This arrest is RAD9-independent. We hypothesize that the Sep1 protein participates directly in meiotic recombination and that other strand exchange enzymes, acting in parallel recombination pathways, are able to substitute partially for the absence of the Sep1 protein.

scholarly journals A Sinorhizobium meliloti Lipopolysaccharide Mutant Induces Effective Nodules on the Host Plant Medicago sativa (Alfalfa) but Fails to Establish a Symbiosis with Medicago truncatula

1998 ◽  
Vol 11 (9) ◽  
pp. 906-914 ◽  
Author(s):  
K. Niehaus ◽  
A. Lagares ◽  
A. Pühler
Keyword(s):  
Sinorhizobium Meliloti ◽  
Uv Light ◽  
Root Nodules ◽  
Sodium Dodecyl ◽  
Microscopic Analysis ◽  
Wild Type ◽  
Electron Microscopic ◽  
Molecular Weights ◽  
Infection Threads ◽  
Dna Fragment

The specific Sinorhizobium meliloti lipopolysaccharide (LPS) mutant Rm6963 (A. Lagares, G. Caetano Anolles, K. Niehaus, J. Lorenzen, H. D. Ljunggren, A. Puhler, and G. Favelukes, J. Bacteriol. 174:5941-5952, 1992) was shown to be mutated in a region corresponding to a cloned 5-kb SstI DNA fragment that was able to complement the lpsB and lpsC mutants of S. meliloti described by Clover et al. (R. H. Clover, J. Kieber, and E. R. Signer, J. Bacteriol. 171:3961-3967, 1989). Sodium dodecyl sulfate polyacryla-mide electrophoresis revealed that the LPS-I and LPS-II fractions of the LPS mutant Rm6963 were shifted to lower molecular weights. While the majority of the Medicago spp. tested established an effective symbiosis with both the S. meliloti wild-type Rm2011 and the LPS mutant Rm6963, the latter induced ineffective nodules on M. truncatula. A light- and electron-microscopic analysis of the ineffective M. truncatula root nodules revealed that the bacteria were released from the infection threads but failed to colonize the plant cells effectively. The plant cytoplasm was filled with numerous vesicles, probably the result of a disturbed bacteroid development. Sections of ineffective M. truncatula root nodules induced by the LPS mutant Rm6963 showed brown, necrotic cells within the central nodule tissue that autofluoresced when viewed under UV light. These observations are best explained by a plant defense response. Evidently, the rhizobial LPS plays a role in plant-microbe signaling during the formation of M. truncatula nodules.

Retinal degeneration in the nervous mutant mouse. II. Electron microscopic analysis

1993 ◽  
Vol 333 (2) ◽  
pp. 182-198 ◽  
Author(s):  
Mary P. White ◽  
Gregg M. Gorrin ◽  
Richard J. Mullen ◽  
Matthew M. LaVail
Keyword(s):  
Retinal Degeneration ◽  
Mutant Mouse ◽  
Microscopic Analysis ◽  
Electron Microscopic Analysis ◽  
Electron Microscopic

Defective thyroglobulin storage in LDL receptor-associated protein-deficient mice

2006 ◽  
Vol 290 (4) ◽  
pp. C1160-C1167 ◽  
Author(s):  
Simonetta Lisi ◽  
Roberta Botta ◽  
Aldo Pinchera ◽  
A. Bernard Collins ◽  
Samuel Refetoff ◽  
...  
Keyword(s):  
Molecular Chaperone ◽  
Hormone Secretion ◽  
Ldl Receptor ◽  
Normal Serum ◽  
Wild Type ◽  
Histological Features ◽  
Receptor Associated Protein ◽  
Concomitant Reduction ◽  
Deficient Mice ◽  
Serum Tsh

The molecular chaperone receptor-associated protein (RAP) is required for biosynthesis of megalin, an endocytic receptor for follicular thyroglobulin (Tg), the thyroid hormone precursor. RAP also binds to Tg itself, suggesting that it may affect Tg trafficking in various manners. To elucidate RAP function, we have studied the thyroid phenotype in RAP-knockout (RAP-KO) mice and found a reduction of Tg aggregates into thyroid follicles. Serum Tg levels were significantly increased compared with those of wild-type (WT) mice, suggesting a directional alteration of Tg secretion. In spite of these abnormalities, hormone secretion was maintained as indicated by normal serum thyroxine levels. Because Tg in thyroid extracts from RAP-KO mice contained thyroxine residues as in WT mice, we concluded that in RAP-KO mice, follicular Tg, although reduced, was nevertheless sufficient to provide normal hormone secretion. Serum TSH was increased in RAP-KO mice, and although no thyroid enlargement was observed, some histological features resembling early goiter were present. Megalin was decreased in RAP-KO mice, but this did not affect thyroid function, probably because of the concomitant reduction of follicular Tg. In conclusion, RAP is required for the establishment of Tg reservoirs, but its absence does not affect hormone secretion.

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