Effects of mitogen-activated protein kinase signal pathway on heat shock protein 27 expression in human lens epithelial cells exposed to sodium salicylate in vitro

Small heat-shock proteins (sHSPs) are widely expressed 25–28 kDa proteins whose functions are dynamically regulated by phosphorylation. While recent efforts have clearly delineated a stress-responsive p38 mitogen-activated protein-kinase (MAPK)-dependent kinase pathway culminating in activation of the heat-shock (HSP)-kinases, mitogen-activated protein-kinase-activated protein kinase-2 and -3, not all sHSP phosphorylation events can be explained by the p38 MAPK-dependent pathway. The contribution of protein kinase C (PKC) to sHSP phosphorylation was suggested by early studies but later questioned on the basis of the reported poor ability of purified PKC to phosphorylate sHSP in vitro. The current study re-evaluates the role of PKC in sHSP phosphorylation in the light of the isoform complexity of the PKC family. We evaluated the sHSP phosphorylation status in rat corpora lutea obtained from two stages of pregnancy, mid-pregnancy and late-pregnancy, which express different levels of the novel PKC isoform, PKC-δ. Two-dimensional Western blot analysis showed that HSP-27 was more highly phosphorylated in vivo in corpora lutea of late pregnancy, corresponding to the developmental stage in which PKC-δ is abundant and active. Late-pregnant luteal extracts contained a lipid-sensitive HSP-kinase activity which exactly co-purified with PKC-δ using hydroxyapatite and S-Sepharose column chromatography. To determine whether there might be preferential phosphorylation of sHSP by a particular PKC isoform, purified recombinant PKC isoforms corresponding to those PKC isoforms detected in rat corpora lutea were evaluated for HSP-kinase activity in vitro. Recombinant PKC-δ effectively catalysed the phosphorylation of sHSP in vitro, and PKC-α was 30–50% as effective as an HSP-kinase; other PKCs tested (β1, β2, ε and ζ) were poor HSP-kinases. These results show that select PKC family members can function as direct HSP-kinases in vitro. Moreover, the observation of enhanced luteal HSP-27 phosphorylation in vivo, in late pregnancy, when PKC-δ is abundant and active, suggests that select PKC family members contribute to sHSP phosphorylation events in vivo.

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Enhanced developmental potential of heat-shocked porcine parthenogenetic embryos is related to accelerated mitogen-activated protein kinase dephosphorylation

Reproduction Fertility and Development ◽

10.1071/rd08268 ◽

2009 ◽

Vol 21 (7) ◽

pp. 892 ◽

Cited By ~ 3

Author(s):

S. Clay Isom ◽

Randall S. Prather ◽

Edmund B. Rucker III

Keyword(s):

Heat Shock ◽

Protein Kinase ◽

Elevated Temperatures ◽

Mitogen Activated Protein Kinase ◽

Oocyte Activation ◽

Developmental Potential ◽

Mapk Activity ◽

Mitogen Activated Protein ◽

Parthenogenetic Embryos

Recently, we demonstrated that a 9-h heat shock of 42°C can have marked stimulatory effects on porcine parthenogenetic embryo development if applied immediately after oocyte activation. Developmental discrepancies between heat-shocked (HS) and non-HS embryos were manifest as early as 3 h after activation, suggesting involvement of maturation promoting factor (MPF) and/or mitogen-activated protein kinase (MAPK). Analysis of cdc2 kinase activity showed that MPF inactivation occurred at similar rates in HS and control embryos upon oocyte activation. However, MAPK dephosphorylation was accelerated in HS embryos compared with controls. Okadaic acid, a protein phosphatase inhibitor, maintained MAPK activity at high levels in both non-HS and HS embryos and sensitised HS embryos to the effects of elevated temperatures. No increase in heat shock proteins was observed in pronuclear-stage HS embryos. These data suggest that the acceleration of development observed in HS porcine parthenogenetic embryos is associated with a precocious inactivation of the MAPK signalling cascade. The faster cleavage divisions observed in HS embryos may be linked physiologically to their enhanced developmental potential in vitro.

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P 229 Growth of human lens epithelial cells on the anterior lens capsule in vitro

Vision Research ◽

10.1016/0042-6989(95)90545-6 ◽

1995 ◽

Vol 35 ◽

pp. S199

Author(s):

J.H. Meyer ◽

J. Schmidt ◽

F. Eppinger ◽

B. Flügel ◽

K.U. Löffler ◽

...

Keyword(s):

Epithelial Cells ◽

Lens Capsule ◽

Human Lens ◽

Lens Epithelial Cells ◽

Human Lens Epithelial Cells ◽

Anterior Lens Capsule

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Nanoceria Prevents Glucose-Induced Protein Glycation in Eye Lens Cells

Nanomaterials ◽

10.3390/nano11061473 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1473

Author(s):

Belal I. Hanafy ◽

Gareth W. V. Cave ◽

Yvonne Barnett ◽

Barbara K. Pierscionek

Keyword(s):

Protein Glycation ◽

Human Lens ◽

Lens Epithelial Cells ◽

Oxide Nanoparticles ◽

Lens Protein ◽

Oxygen Species ◽

Human Lens Epithelial Cells ◽

Age Related ◽

Age Related Changes

Cerium oxide nanoparticles (nanoceria) are generally known for their recyclable antioxidative properties making them an appealing biomaterial for protecting against physiological and pathological age-related changes that are caused by reactive oxygen species (ROS). Cataract is one such pathology that has been associated with oxidation and glycation of the lens proteins (crystallins) leading to aggregation and opacification. A novel coated nanoceria formulation has been previously shown to enter the human lens epithelial cells (HLECs) and protect them from oxidative stress induced by hydrogen peroxide (H2O2). In this work, the mechanism of nanoceria uptake in HLECs is studied and multiple anti-cataractogenic properties are assessed in vitro. Our results show that the nanoceria provide multiple beneficial actions to delay cataract progression by (1) acting as a catalase mimetic in cells with inhibited catalase, (2) improving reduced to oxidised glutathione ratio (GSH/GSSG) in HLECs, and (3) inhibiting the non-enzymatic glucose-induced glycation of the chaperone lens protein α-crystallin. Given the multifactorial nature of cataract progression, the varied actions of nanoceria render them promising candidates for potential non-surgical therapeutic treatment.

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Cross-talk between IRAK-4 and the NADPH oxidase1

Biochemical Journal ◽

10.1042/bj20061184 ◽

2007 ◽

Vol 403 (3) ◽

pp. 451-461 ◽

Cited By ~ 50

Author(s):

Sandrine Pacquelet ◽

Jennifer L. Johnson ◽

Beverly A. Ellis ◽

Agnieszka A. Brzezinska ◽

William S. Lane ◽

...

Keyword(s):

Protein Kinase ◽

Nadph Oxidase ◽

P38 Mapk ◽

Interleukin 1 ◽

Mitogen Activated Protein Kinase ◽

Free System ◽

Mitogen Activated Protein ◽

A Cell ◽

Tlr4 Activation

Exposure of neutrophils to LPS (lipopolysaccharide) triggers their oxidative response. However, the relationship between the signalling downstream of TLR4 (Toll-like receptor 4) after LPS stimulation and the activation of the oxidase remains elusive. Phosphorylation of the cytosolic factor p47phox is essential for activation of the NADPH oxidase. In the present study, we examined the hypothesis that IRAK-4 (interleukin-1 receptor-associated kinase-4), the main regulatory kinase downstream of TLR4 activation, regulates the NADPH oxidase through phosphorylation of p47phox. We show that p47phox is a substrate for IRAK-4. Unlike PKC (protein kinase C), IRAK-4 phosphorylates p47phox not only at serine residues, but also at threonine residues. Target residues were identified by tandem MS, revealing a novel threonine-rich regulatory domain. We also show that p47phox is phosphorylated in granulocytes in response to LPS stimulation. LPS-dependent phosphorylation of p47phox was enhanced by the inhibition of p38 MAPK (mitogen-activated protein kinase), confirming that the kinase operates upstream of p38 MAPK. IRAK-4-phosphorylated p47phox activated the NADPH oxidase in a cell-free system, and IRAK-4 overexpression increased NADPH oxidase activity in response to LPS. We have shown that endogenous IRAK-4 interacts with p47phox and they co-localize at the plasma membrane after LPS stimulation, using immunoprecipitation assays and immunofluorescence microscopy respectively. IRAK-4 was activated in neutrophils in response to LPS stimulation. We found that Thr133, Ser288 and Thr356, targets for IRAK-4 phosphorylation in vitro, are also phosphorylated in endogenous p47phox after LPS stimulation. We conclude that IRAK-4 phosphorylates p47phox and regulates NADPH oxidase activation after LPS stimulation.

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