The generation and characterization of a transgenic zebrafish line with lens-specific Cre expression.

Purpose: Danio rerio zebrafish constitute a popular model for studying lens development and congenital cataracts. However, the specific deletion of a gene with a Cre/LoxP system in the zebrafish lens is unavailable because of the lack of a lens-Cre-transgenic zebrafish. This study aimed to generate a transgenic zebrafish line in which Cre recombinase was specifically expressed in the lens. Methods: The pTol2 cryaa:Cre-polyA-cryaa:EGFP (enhanced green fluorescent protein) plasmid was constructed and co-injected with Tol2-transposase into one-to-two-cell-stage wild-type (WT) zebrafish embryos. Whole-mount in situ hybridization (ISH), tissue section, hematoxylin and eosin staining, a Western blot, a split-lamp observation, and a grid transmission assay were used to analyze the Cre expression, lens structure, and lens transparency of the transgenic zebrafish. Results: In this study, we generated a transgenic zebrafish line, zTg(cryaa:Cre-cryaa:EGFP), in which Cre recombinase and EGFP were driven by the lens-specific cryaa promoter. zTg(cryaa:Cre-cryaa:EGFP) began to express Cre and EGFP specifically in the lens at the 22 hpf stage, and this ectopic Cre could efficiently and specifically delete the red fluorescent protein (RFP) signal from the lens when zTg(cryaa:Cre-cryaa:EGFP) embryos were injected with the loxP-flanked RFP plasmid. The overexpression of Cre and EGFP did not impair zebrafish development or lens transparency. Accordingly, this zTg(cryaa:Cre-cryaa:EGFP) zebrafish line is a useful tool for gene editing, specifically with zebrafish lenses. Conclusions: We established a zTg(cryaa:Cre-cryaa:EGFP) zebrafish line that can specifically express an active Cre recombinase in lens tissues. This transgenic zebrafish line can be used as a tool to specifically manipulate a gene in zebrafish lenses.

The downregulation of HSP90-controlled CRALBP expression is associated with age-related vision attenuation.

The dysfunction of CRALBP, a key regulator of the visual cycle, is associated with retinitis punctata albescens characterized by night vision loss and retinal degeneration. In this paper, we find that the expression of CRALBP is regulated by heat shock protein 90 (HSP90). Inhibition of HSP90α or HSP90ß expression by using the CRISPR-Cas9 technology downregulates CRALBP's mRNA and protein expression in ARPE-19 cells by triggering the degradation of transcription factor SP1 in the ubiquitin-proteasome pathway. SP1 can bind to CRALBP's promoter, and inhibition of SP1 by its inhibitor plicamycin or siRNA downregulates CRALBP's mRNA expression. In the zebrafish, inhibition of HSP90 by the intraperitoneal injection of IPI504 reduces the thickness of the retinal outer nuclear layer and Rlbp1b mRNA expression. Interestingly, the expression of HSP90, SP1, and CRALBP is correlatedly downregulated in the senescent ARPE-19 and Pig primary RPE cells in vitro and in the aged zebrafish and mouse retinal tissues in vivo. The aged mice exhibit the low night adaption activity. Taken together, these data indicate that the HSP90-SP1 is a novel regulatory axis of CRALBP transcriptional expression in RPE cells. The age-mediated downregulation of the HSP90-SP1-CRALBP axis is a potential etiology for the night vision reduction in senior people.

Knockout of miR-184 in zebrafish leads to ocular abnormalities by elevating p21 levels.

miR-184 is one of the most abundant miRNAs expressed in the lens and corneal tissue. Mutations in the seed region of miR-184 are responsible for inherited anterior segment dysgenesis. Animal models recapitulating miR-184-related anterior segment dysgenesis are still lacking, and the molecular basis of ocular abnormalities caused by miR-184 dysfunction has not been well elucidated in vivo. In the present study, we constructed a miR-184-/- zebrafish line by destroying both two dre-mir-184 paralogs with CRISPR-Cas9 technology. Although there were no gross developmental defects, the miR-184-/- zebrafish displayed microphthalmia and cataract phenotypes. Cytoskeletal abnormalities, aggregation of γ-crystallin, and lens fibrosis were induced in miR-184-/- lenses. However, no obvious corneal abnormalities were observed in miR-184-/- zebrafish. Instead of apoptosis, deficiency of miR-184 led to aberrant cell proliferation and a robust increase in p21 levels in zebrafish eyes. Inhibition of p21 by UC2288 compromised the elevation of lens fibrosis markers in miR-184-/- lenses. RNA-seq demonstrated that levels of four transcriptional factors HSF4, Sox9a, CTCF, and Smad6a, all of which could suppress p21 expression, were reduced in miR-184-/- eyes. The predicted zebrafish miR-184 direct target genes (e.g., atp1a3a and nck2a) were identified and verified in miR-184-/- eye tissues. The miR-184-/- zebrafish is the first animal model mimicking miR-184-related anterior segment dysgenesis and could broaden our understanding of the roles of miR-184 in eye development.

Extracellular HSP90 promotes differentiation of lens epithelial cells to fiber cells by activating LRP1-YAP-PROX1 axis.

Capsular residual lens epithelial cells (CRLEC) undergo differentiation to fiber cells for lens regeneration or tansdifferentiation to myofibroblasts leading to posterior capsular opacification (PCO) after cataract surgery. The underlying regulatory mechanism remains unclear. Using human lens epithelial cell lines and the ex vivo cultured rat lens capsular bag model, we found that the lens epithelial cells secrete HSP90α extracellularly (eHSP90) through an autophagy-associated pathway. Administration of recombinant GST-HSP90α protein or its M-domain induces the elongation of rat CRLEC cells with concomitant upregulation of the crucial fiber cell transcriptional factor PROX1and its downstream targets, ß- and γ-crystallins and structure proteins. This regulation is abolished by PROX1 siRNA. GST-HSP90α upregulates PROX1 by binding to LRP1 and activating LRP1-AKT mediated YAP degradation. The upregulation of GST-HSP90α on PROX1 expression and CRLEC cell elongation is inhibited by LRP1 and AKT inhibitors, but activated by YAP-1 inhibitor (VP). These data demonstrated that the capsular residue epithelial cells upregulate and secrete eHSP90α, which in turn drive the differentiation of lens epithelial cell to fiber cells. The recombinant HSP90α protein is a potential novel differentiation regulator during lens regeneration.

SARS-COV-2 spike protein promotes RPE cell senescence via the ROS/P53/P21 pathway.

SARS-Cov-2 infection, which has caused the COVID-19 global pandemic, triggers cellular senescence. In this study, we investigate the role of the SARS-COV-2 spike protein (S-protein) in regulating the senescence of RPE cells. The results showed that administration or overexpression of S-protein in ARPE-19 decreased cell proliferation with cell cycle arrest at the G1 phase. S-protein increased SA-ß-Gal positive ARPE-19 cells with high expression of P53 and P21, senescence-associated inflammatory factors (e.g., IL-1ß, IL-6, IL-8, ICAM, and VEGF), and ROS. Elimination of ROS by N-acetyl cysteine (NAC) or knocking down p21 by siRNA diminished S-protein-induced ARPE cell senescence. Both administrated and overexpressed S-protein colocalize with the ER and upregulate ER-stress-associated BIP, CHOP, ATF3, and ATF6 expression. S-protein induced P65 protein nuclear translocation. Inhibition of NF-κB by bay-11-7082 reduced S-protein-mediated expression of senescence-associated factors. Moreover, the intravitreal injection of S-protein upregulates senescence-associated inflammatory factors in the zebrafish retina. In conclusions, the S-protein of SARS-Cov-2 induces cellular senescence of ARPE-19 cells in vitro and the expression of senescence-associated cytokines in zebrafish retina in vivo likely by activating ER stress, ROS, and NF-κb. These results may uncover a potential association between SARS-cov-2 infection and development of AMD.

Crosstalk between heat shock factor 1 and signal transducer and activator of transcription 3 mediated by interleukin-8 autocrine signaling maintains the cancer stem cell phenotype in liver cancer.

BACKGROUND AND AIM: Liver cancer stem cells (LCSCs) cause therapeutic refractoriness and relapse in hepatocellular carcinoma. Heat shock factor 1 (HSF1) plays versatile roles in multiple cancers. However, the role of HSF1 in LCSCs is not well understood. This study investigated the function and signal mechanisms of HSF1 in maintaining LCSC phenotypes. METHODS: We established two LCSC lines, HepG2-R and HuH-7-R. Constitutive activation of HSF1 was observed in these LCSCs. Specific short hairpin RNAs (shRNAs) and chemical inhibitors were used to identify the relationship between HSF1 expression and LCSCs phenotypes. RESULTS: We revealed a concomitant activation modality involving HSF1 and STAT3 in LCSCs and liver cancer tissues. We also found that liver cancer patients whose HSF1 and STAT3 mRNA expression levels were high presented with unfavorable clinicopathological characteristics. Moreover, the secretion of interleukin-8 (IL-8) was elevated in the LCSC medium and was directly regulated by HSF1 at the transcriptional level. In turn, IL-8 activated HSF1 and STAT3 signaling, and a neutralizing IL-8 antibody inhibited HSF1 and STAT3 activity, reduced cancer stem cell marker expression, and decreased LCSC microsphere formation. Simultaneous intervention with HSF1 and STAT3 led to synergistically suppressed stemness acquisition and growth suppression in the LCSCs in vivo and in vitro. CONCLUSIONS: Our study indicates that IL-8 mediates the crosstalk between the HSF1 and Stat3 signaling pathways in LCSCs and that the combined targeting of HSF1 and STAT3 is a promising treatment strategy for patients with advanced liver cancer.

Retinitis pigmentosa 2 pathogenic mutants degrade through BAG6/HUWE1 complex.

Retinitis pigmentosa (RP) is the most common inherited retinal degenerative disease which is the major cause of vision loss. X-linked RP patients account for 5%-15% of all inherited RP cases and mutations in RP2 (Retinitis pigmentosa 2) were responsible for about 20% X-linked RP families. A majority of RP2 pathogenic mutations displayed a vulnerable protein stability and degraded rapidly through ubiquitin-proteasome system (UPS). Though the RP2 protein could be readily recovered by proteasome inhibitors, e.g., MG132, their applications for RP2-related RP therapy were limited by their nonspecific characterization. In the present study, we aimed to identify UPS-related factors, such as E3 ligases, which are specifically involved in degradation of RP2 pathogenic mutants. We identified several E3 ligases, such as HUWE1, and the co-chaperon BAG6 specifically interacting with RP2 pathogenic mutants. Knockdown of HUWE1 and BAG6 could partially rescue the reduced protein levels of RP2 mutants. BAG6 is required for recruitment of HUWE1 to ubiquitinate RP2 mutants at the K268 site. The HUWE1 inhibitor BI8622 could restore the levels of RP2 mutant and then the binding to its partner ARL3 in retina cell lines. This study revealed the details of UPS-related degradation of RP2 mutants and possibly provided a potential treatment for RP2-related RP.

FcRn is not the receptor mediating the transfer of serum IgG to colostrum in pigs.

In contrast to humans or rabbits, in which maternal IgG is transmitted to offspring prenatally via the placenta or the yolk sac, large domestic animals such as pigs, cows and sheep transmit IgG exclusively through colostrum feeding after delivery. The extremely high IgG content in colostrum is absorbed by newborns via the small intestine. Although it is widely accepted that the neonatal Fc receptor, FcRn, is the receptor mediating IgG transfer across both the placenta and small intestine, it remains unclear whether FcRn also mediates serum IgG transfer across the mammary barrier to colostrum/milk, especially in large domestic animals. In this study, using a FcRn knockout pig model generated with a CRISPR-Cas9-based approach, we clearly demonstrate that FcRn is not responsible for the IgG transfer from serum to colostrum in pigs, although like in other mammals, it is involved in IgG homeostasis and mediates IgG absorption in the small intestine of newborns.

The engineered expression of secreted HSPB5-Fc in CHO cells exhibits cytoprotection in vitro.

BACKGROUND: HSPB5 is an ATP-independent molecular chaperone that is induced by heat shock or other proteotoxic stresses. HSPB5 is cytoprotective against stress both intracellularly and extracellularly. It acts as a potential therapeutic candidate in ischemia-reperfusion and neurodegenerative diseases. RESULTS: In this paper, we constructed a recombinant plasmid that expresses and extracellularly secrets a HSPB5-Fc fusion protein (sHSPB5-Fc) at 0.42 µg/ml in CHO-K1 cells. This sHSPB5-Fc protein contains a Fc-tag at the C-terminal extension of HSPB5, facilitating protein-affinity purification. Our study shows that sHSPB5-Fc inhibits heat-induced aggregation of citrate synthase in a time and dose dependent manner in vitro. Administration of sHSPB5-Fc protects lens epithelial cells against cisplatin- or UVB-induced cell apoptosis. It also decreases GFP-Httex1-Q74 insolubility, and reduces the size and cytotoxicity of GFP-Httex1-Q74 aggregates in PC-12 cells. CONCLUSION: This recombinant sHSPB5-Fc exhibits chaperone activity to protect cells against proteotoxicity.

Differentially expressed microRNAs in the aqueous humor of patients with exfoliation glaucoma or primary open-angle glaucoma.

Both exfoliation glaucoma (XFG) and primary open-angle glaucoma (POAG) have been linked to decreased conventional outflow of aqueous humor (AH). To better understand the molecular changes in the AH content under such conditions, we analyzed the miRNA profiles of AH samples from patients with POAG and XFG compared to non-glaucoma controls. Individual AH samples (n = 76) were collected from POAG and XFG patients and age-matched controls during surgical procedure. After RNA extraction, the miRNA profiles were individually determined in 12 POAG, 12 XFG and 11 control samples. We identified 205, 295 and 195 miRNAs in the POAG, XFG and control samples, respectively. Our differential expression analysis identified three miRNAs (miR-125b-5p, miR-302d-3p and miR-451a) significantly different between POAG and controls, five miRNAs (miR-122-5p, miR-3144-3p, miR-320a, miR-320e and miR-630) between XFG and controls and one miRNA (miR-302d-3p) between POAG and XFG. While none of these miRNAs have been previously linked to glaucoma, miR-122-5p may target three glaucoma-associated genes: OPTN, TMCO1 and TGF-ß1. Pathway analysis revealed that these miRNAs are involved in potential glaucoma pathways, including focal adhesion, tight junctions, and TGF-ß signaling. Comparison of the miRNA profile in AH to unrelated human serum (n = 12) exposed potential relationships between these two fluids, although they were not significantly correlated. In summary, we have successfully profiled the miRNA expression without amplification in individual human AH samples and identified several POAG or XFG-associated miRNAs. These miRNAs may play a role in pathways previously implicated in glaucoma and act as biomarkers for disease pathogenesis.

RNA interference may suppress stress granule formation by preventing argonaute 2 recruitment.

RNA-induced silencing complex (RISC) is formed during RNA interference (RNAi), whereas stress granules (SG) are assembled in response to cellular stress. Here, we demonstrate an interesting connection between RISC and SG that may involve argonaute 2 (Ago2), a core component of RISC. We analyzed SG induction by arsenite, the commonly used SG inducer. SG formation was suppressed in heat shock transcription factor 1 (Hsf1) or hypoxia-inducible factor-1α (Hif1α) shRNA-transfected cells but not in Hsf1 or Hif1α-knockout cells, suggesting that RNAi per se (rather than gene deficiency) may account for the suppressive effect on SG. In support, the suppressive effect of RNAi on SG formation was reversed by the RISC-loading inhibitor aurintricarboxylic acid. In non-RNAi cells, arsenite induced the accumulation of Ago2 in SGs as shown by its colocalization and coimmunoprecipitation with SG proteins, but Ago2 was not recruited to SG in the cells with RNAi. Consistently, arsenite induced the dissociation of Ago2 from RISC proteins in non-RNAi cells but not in RNAi cells. CRISPR-Cas9-medicated ablation of Ago2 attenuated SG formation during arsenite treatment, suggesting a critical role of Ago2 in SG assembly. Together, these results indicate that RISC and SG may compete for some key components, such as Ago2. In response to cellular stress, Ago2 is recruited for SG assembly; however, during RNAi, Ago2 is held in RISC, becoming unavailable for SG formation.

HSP90 as a novel therapeutic target for posterior capsule opacification.

Posterior capsule opacification (PCO) is a common complication of cataract surgery, resulting from a combination of proliferation, migration, epithelial-mesenchymal transition (EMT) of residual capsular epithelial cells and fibrosis of myofibroblasts. HSP90 is known to regulate the proteostasis of cells under pathophysiological conditions. The role of HSP90 in PCO formation, however, is not clear. To do this, the lens epithelial cell lines and an ex vivo cultured rat capsular bag model were used to study the role of HSP90 in PCO formation. The expression of protein and mRNA was measured by immunoblotting and quantitative RT-PCR, and cell apoptosis was measured by TUNEL(TdT-mediated dUTP nick-end labeling). The cell proliferation was measured by cell viability assays. The results showed that 17-AAG (Tanespimycin), an inhibitor of HSP90, suppresses the proliferation of immortalized lens epithelial cell lines HLE-B3, SRA01/04, and mLEC, with IC50 values of 0.27, 0.27, and 0.49 µM, respectively. In an ex vivo cultured rat capsular model, the capsular residual epithelial cells resisted the stress of the capsulorhexis surgery and took 3-6 days to completely overlay the capsular posterior wall. During this process, heat shock factor 1 and its downstream targets HSP90, HSP25, αB-crystallin, and HSP40 were upregulated. Treatment with 17-AAG inhibited the viability of capsular residual epithelial cells and induced the cells apoptosis, characterized by increases in ROS levels, apoptotic DNA injury, and the activation of caspases 9 and 3. HSP90 participated in regulating both EGF receptor (EGFR) and TGF receptor (TGFR) signaling pathways. HSP90 was found to interact with the EGFR, such that inhibition of HSP90 by 17-AAG destabilized the EGFR protein and suppressed p-ERK1/2 and p-AKT levels. 17-AAG also inhibited the TGF-ß-induced phosphorylation of SMAD2/3 and ERK1/2 and the decrease in E-cadherin and ZO-1 expression. Accordingly, these data suggest that the induction of HSP90 protects capsular residual epithelial cells against capsulorhexis-induced stress and participates in regulating the processes of proliferation, EMT and migration of rat capsular residual epithelial cells, at least partly, through the EGFR and TGFR signaling pathways. Treatment with 17-AAG suppresses PCO formation and is therefore a potential therapeutic candidate for PCO prevention.

Hsf4 counteracts Hsf1 transcription activities and increases lens epithelial cell survival in vitro.

The interplay between Hsf4 and Hsf1 plays an important role in the regulation of lens homeostasis. However, the mechanism of the intermolecular association involved is still unclear. In this paper, we find that reconstitution of Hsf4b into Hsf4-/- lens epithelial (mLEC/Hsf4-/-) cells can simultaneously downregulate Hsp70 expression and upregulate the expression of small heat shock proteins Hsp25 and αB-crystallin at both RNA and protein levels. ChIP assay results indicate Hsf4b, which binds to the promoters of Hsp90α, Hsp70.3, Hsp25 and αB-crystallin but not Hsp70.1, can inhibit Hsf1 binding to Hsp70.3 promoter and the heat shock mediated Hsp70 promoter activity by reducing Hsf1 protein expression. Hsf4b N-terminal hydrophobic region can interact with Hsf1 N-terminal hydrophobic region. Their interaction impairs Hsf1's intramolecular interaction between the N- and C-terminal hydrophobic regions, leading to Hsf1's cytosolic retention and protein degradation. Both lysosome inhibitors (chloroquine, pepstatin A plus E64d) and proteasome inhibitor MG132 can inhibit Hsf4-mediated Hsf1 protein degradation, but MG132 can induce Hsf1 activation as well. Upregulation of Hsf4b can significantly inhibit cisplatin and staurosporine induced lens epithelial cell apoptosis through direct upregulation of Hsp25 and αB-crystallin expression. Taken together, our results imply that upregulation of Hsf4b modulates the expression pattern of heat shock proteins in lens tissue by either directly binding to their promoters or promoting Hsf1 protein degradation. Moreover, upregulation of Hsf4b protects lens cell survival by upregulating anti-apoptotic pathways. These studies reveal a novel regulatory mechanism between Hsf1 and Hsf4b in modulating lens epithelial cell homeostasis.

Heat shock factor 1 induces crystallin-αB to protect against cisplatin nephrotoxicity.

Cisplatin, a wildly used chemotherapy drug, induces nephrotoxicity that is characterized by renal tubular cell apoptosis. In response to toxicity, tubular cells can activate cytoprotective mechanisms, such as the heat shock response. However, the role and regulation of the heat shock response in cisplatin-induced nephrotoxicity remain largely unclear. In the present study, we demonstrated the induction of heat shock factor (Hsf)1 and the small heat shock protein crystallin-αB (CryAB) during cisplatin nephrotoxicity in mice. Consistently, cisplatin induced Hsf1 and CryAB in a cultured renal proximal tubular cells (RPTCs). RPTCs underwent apoptosis during cisplatin treatment, which was increased when Hsf1 was knocked down. Transfection or restoration of Hsf1 into Hsf1 knockdown cells suppressed cisplatin-induced apoptosis, further supporting a cytoprotective role of Hsf1 and its associated heat shock response. Moreover, Hsf1 knockdown increased Bax translocation to mitochondria and cytochrome c release into the cytosol. In RPTCs, Hsf1 knockdown led to a specific downregulation of CryAB. Transfection of CryAB into Hsf1 knockdown cells diminished their sensitivity to cisplatin-induced apoptosis, suggesting that CryAB may be a key mediator of the cytoprotective effect of Hsf1. Taken together, these results demonstrate a heat shock response in cisplatin nephrotoxicity that is mediated by Hsf1 and CryAB to protect tubular cells against apoptosis.

Regulation of Hsf4b nuclear translocation and transcription activity by phosphorylation at threonine 472.

Hsf4b, a key regulator of postnatal lens development, is subjected to posttranslational modifications including phosphorylation. However, the phosphorylation sites in Hsf4b and their biological effects on the transcription activity of Hsf4b are poorly understood. Here we examined 17 potential phosphorylation residues in Hsf4b with alanine-scanning assays and found that a T472A mutation diminished Hsf4b-mediated expression of Hsp25 and alphaB-crystallin. In contrast, the phosphomimetic mutation of T472D enhanced their expression. Further investigation demonstrated that Hsf4b could interact with nuclear-transporter importin beta-1 and Hsc70 via amino acids 246-320 and 320-493, respectively. T472A mutation reduced Hsf4bs interaction with importin beta-1, while enhancing its interaction with Hsc7O, resulting in Hsf4b cytosolic re-localization, protein instability and transcription activity attenuation. At the upstream, MEK6 was found to interact with Hsf4b and enhance Hsf4b's nuclear translocation and transcription activity, probably by phosphorylation at sites such as T472. Taken together, our results suggest that phosphotylation of Hsf4b at T472 by protein kinases such as MEI(6 regulates Hsf4b interaction with the importin V I -Hsc7O complex, resulting in blockade of its nuclear translocation and transcriptional activity of Hsf4b.

Glucose regulates heat shock factor 1 transcription activity via mTOR pathway in HCC cell lines.

HSF1-mediated heat shock response is activated in most tumors and plays important roles in regulating tumor homeostasis. However, the signals underlying HSF1 activation is still not completely understood. In this paper, we find that glucose, the dominant tumor energy supplement, participates in regulating HSF1's activation in HCC cell lines. The immunoblotting results indicate that the phosphorylation of HSF1/S326, a hallmark of HSF1 activation, varies between the HCC cell lines (e.g., SMMC7721, HapG2, plc/prf5, and Chang-liver). Glucose, but not 2D-glucose, can induce the phosphorylation of HSF1 at S326 and upregulate the expression of HSF1's downstream alpha B-crystallin and Hsp70 as well as the none-heat shock proteins CSK2 and RBM23 in two tested hepatocellular carcinoma cell lines (prl/prf5 and SMMC7721). Rapamycin, an inhibitor of mTOR, can suppress the glucose-induced phosphorylation of HSF1/S326 and the expression of alpha B-crystallin. Knockdown of HSF1 with shRNA enhances the glucose-depletion-mediated inhibition of plc/prf5 cell proliferation. Our data reveal that HSF1 can be activated by glucose-mTOR pathway, providing an alternative pathway for targeting HSF1 in tumor therapy.

OMA1 mediates OPA1 proteolysis and mitochondrial fragmentation in experimental models of ischemic kidney injury.

Acute kidney injury (AKI) is associated with mitochondrial fragmentation, which contributes to mitochondrial damage and tubular cell apoptosis. Mitochondrial fragmentation involves the cleavage of both mitochondrial outer and inner membranes. Cleavage of the outer membrane results from Drp-1-mediated fission activation and Bak-promoted fusion arrest, but the molecular mechanism of inner membrane cleavage remains elusive. OMA1-mediated proteolysis of OPA1, a key inner membrane fusion protein, was recently suggested to account for inner membrane cleavage during cell stress. In this study, we determined the role of OMA1 in OPA1 proteolysis and mitochondrial fragmentation in experimental models of ischemic AKI. In ATP-depletion injury, knockdown of OMA1 suppressed OPA1 proteolysis, mitochondrial fragmentation, cytochrome c release, and consequent apoptosis in renal proximal tubular cells. In mice, OMA1 deficiency prevented ischemic AKI as indicated by better renal function, less tubular damage, and lower apoptosis. OPA1 proteolysis and mitochondrial injury during ischemic AKI were ameliorated in OMA1-deficient mice. Thus, OMA1-mediated OPA1 proteolysis plays an important role in the disruption of mitochondrial dynamics in ischemic AKI.

Heat shock factor Hsf1 cooperates with ErbB2 (Her2/Neu) protein to promote mammary tumorigenesis and metastasis.

ErbB2/Neu oncogene is overexpressed in 25% of invasive/metastatic breast cancers. We have found that deletion of heat shock factor Hsf1 in mice overexpressing ErbB2/Neu significantly reduces mammary tumorigenesis and metastasis. Hsf1(+/-)ErbB2/Neu(+) tumors exhibit reduced cellular proliferative and invasive properties associated with reduced activated ERK1/2 and reduced epithelial-mesenchymal transition (EMT). Hsf1(+/+)Neu(+) mammary epithelial cells exposed to TGFß show high levels of ERK1/2 activity and EMT; this is associated with reduced expression of E-cadherin and increased expression of Slug and vimentin, a mesenchymal marker. In contrast, Hsf1(-/-)Neu(+) or Hsf1(+/+)Neu(+) cells do not exhibit activated ERK1/2 and show reduced EMT in the presence of TGFß. The ineffective activation of the RAS/RAF/MEK/ERK1/2 signaling pathway in cells with reduced levels of HSF1 is due to the low levels of HSP90 in complex with RAF1 that are required for RAF1 stability and maturation. These results indicate a powerful inhibitory effect conferred by HSF1 downstream target genes in the inhibition of ErbB2-induced breast cancers in the absence of the Hsf1 gene.

[Establishment of mouse lens epithelial cell lines with the genotype of Hsf4-/-].

OBJECTIVE: To establish mouse lens epithelial cell lines with the genotype of Hsf4-/-. METHODS: The expended mouse lens epithelial cells, which were generated from P6 Hsf4-deficient mouse lens epithelia, were immortalized with SV40-T-antigen and named MLEC/Hsf4-/- cell. The expression of alpha A-crystallin was immunoblotted. Hsf4b cDNA was reconstituted by transiently transfection. RESULTS: The SV40-immortalized cells were in adherent growth mode with spindle morphology, pseudopodia, clear nuclear boundary membrane and cytoplasm translucent. Immunoblotting results indicated that the lens biomarker protein alpha A-crystallin was expressed in MLEC/Hsf4-/- cells. Reconstitution of Hsf4b into MLEC/Hsf4-/- cells upregulated the expression of Hsp25. CONCLUSIONS: The SV40-immortalized MLEC/Hsf4-/- cells have the lens epithelial characteristics and could be used as a tool for studying the signal transduction in vitro.

Recent advances in small molecule and peptide inhibitors of glucose-regulated protein 78 for cancer therapy.

Glucose-regulated protein 78 (GRP78) is one of key endoplasmic reticulum (ER) chaperone proteins that regulates the unfolded protein response (UPR) to maintain ER homeostasis. As a core factor in the regulation of the UPR, GRP78 takes a critical part in the cellular processes required for tumorigenesis, such as proliferation, metastasis, anti-apoptosis, immune escape and chemoresistance. Overexpression of GRP78 is closely correlated with tumorigenesis and poor prognosis in various malignant tumors. Targeting GRP78 is regarded as a potentially promising therapeutic strategy for cancer therapy. Although none of the GRP78 inhibitors have been approved to date, there have been several studies of GRP78 inhibitors. Herein, we comprehensively review the structure, physiological functions of GRP78 and the recent progress of GRP78 inhibitors, and discuss the structures, in vitro and in vivo efficacies, and merits and demerits of these inhibitors to inspire further research. Additionally, the feasibility of GRP78-targeting proteolysis-targeting chimeras (PROTACs), disrupting GRP78 cochaperone interactions, or covalent inhibition are also discussed as novel strategies for drugs discovery targeting GRP78, with the hope that these strategies can provide new opportunities for targeted GRP78 antitumor therapy.