We have reported that treatment with CdCl 2 at 40 -100 M induces the heat shock proteins (HSPs) in 9L rat brain tumor cells, during which the activation of heat shock factor (HSF) is essentially involved. By exploiting protein kinase inhibitors, we further analyzed the possible participation of specific protein kinases in the above processes. It was found that induction of HSP70 in cells treated with a high concentration of cadmium (i.e. 100 M) is preceded by the phosphorylation and activation of p38 mitogen-activated protein kinase (p38 MAPK ), while that in cells treated with a low concentration (60 M) is accompanied by the phosphorylation and activation of extracellular-regulated protein kinases 1 and 2 (ERK1/2). In 100 M cadmium-treated cells, both HSP70 induction and HSF1 activation are eliminated in the presence of SB203580, a specific inhibitor of p38 MAPK . By contrast, in 60 M cadmium-treated cells, the processes are not affected by SB203580 but are significantly suppressed by PD98059, which indirectly inhibits ERK1/2 by acting on MAPK-ERK kinase. Taken together, we demonstrate that p38 MAPK and ERK1/2 can be simultaneously or independently activated under different concentrations of cadmium and that the signaling pathways participate in the induction of HSP70 by acting on the inducible phosphorylation of HSF1. We thus provide the first evidence that both p38 MAPK and ERK signaling pathways can differentially participate in the activation of HSF1, which leads to the induction of HSP70 by cadmium.Heat shock proteins (HSPs) 1 are induced in cells responding to suboptimal growing conditions (1, 2). Transactivation of the heat shock genes has been centered on the interaction of the HSFs with the HSEs, which are found in all heat shock genes (3-5). Although several members of HSF have been characterized, HSF1 has been demonstrated to be the most crucial transcription factor activated in mammalian cells responding to classical inducers of the heat shock response (5-7). Under normal growing conditions, HSF1 may exist as a latent monomeric form, with neither DNA binding nor transcription activity. Activation of HSF1 is through a multistep pathway, a nuclear localization and trimerization step by which HSF1 acquires the properties of a stable trimer, which correlates with the DNA binding activity, and a phosphorylation step by which HSF1 becomes transcriptionally active (5,8,9). On the other hand, HSF1 may also be constitutively phosphorylated, which represses its transcription activity (10, 11). Thus, HSF1 may be constitutively or inducibly phosphorylated, and only inducible phosphorylation of this factor can confer the transcription activity. Several phosphorylation sites in HSF1 have been identified to contain the consensus sequence for proline-directed kinases including ERK1/2, p38 MAPK , and SAPKs, which can efficiently phosphorylate HSF1 in vitro (11,12). However, it is still unclear whether the MAPKs phosphorylate HSF1 in vivo.MAPKs are proline-directed serine/threonine kinases and are themselves activa...

Summary The molecular mechanism behind what causes an infection of Enterovirus 71 (EV71) in young childrento result in severe neurological diseases is unclear. Herein, we show that Cdk5, a critical signalling effector of various neurotoxic insults in the brain, is activated by EV71 infection of neuronal cells. EV71-induced neuronal apoptosis could be effectively repressed by blocking either Cdk5 kinase activity or its protein expression. Moreover, EV71-induced Cdk5 activation was modulated by c-Abl. The suppression of c-Abl kinase activity by STI571 notably repressed both the Cdk5 activation and neuronal apoptosis in cells infected with EV71. Although EV71 also induces apoptosis in non-neuronal cells, it did not affect Abl and Cdk5 activities in several non-neuronal cell lines. Intriguingly, coxsackievirus A16 (CA16), a genetically closely related serotype to EV71 that usually does not induce severe neurological disorders, could only weakly stimulate Abl, but not Cdk5 kinase activity. Taken together, our data suggest a serotype-and cell type-specific mechanism, by which EV71 induces Abl kinase activity, which in turn triggers Cdk5-signalling for neuronal apoptosis.

The need for a new anti-Staphylococcus aureus therapy that can effectively cripple bacterial infection, neutralize secretory virulence factors, and lower the risk of creating bacterial resistance is undisputed. Here, we propose what is, to our knowledge, a previously unreported infectious mechanism by which S. aureus may commandeer Propionibacterium acnes, a key member of the human skin microbiome, to spread its invasion and highlight two secretory virulence factors (S. aureus β-hemolysin and P. acnes CAMP (Christie, Atkins, Munch-Peterson) factor) as potential molecular targets for immunotherapy against S. aureus infection. Our data demonstrate that the hemolysis and cytolysis by S. aureus were noticeably augmented when S. aureus was grown with P. acnes. The augmentation was significantly abrogated when the P. acnes CAMP factor was neutralized or β-hemolysin of S. aureus was mutated. In addition, the hemolysis and cytolysis of recombinant β-hemolysin were markedly enhanced by recombinant CAMP factor. Furthermore, P. acnes exacerbated S. aureus-induced skin lesions in vivo. The combination of CAMP factor neutralization and β-hemolysin immunization cooperatively suppressed the skin lesions caused by coinfection of P. acnes and S. aureus. These observations suggest a previously unreported immunotherapy targeting the interaction of S. aureus with a skin commensal.

Mitochondrial dynamics including morphological fission and mitochondrial movement are essential to normal mitochondrial and cellular physiology. This study investigated how mtDNA T8993G (NARP)-induced inhibition of mitochondrial complex V altered mitochondrial dynamics in association with a protective mitochondrial phospholipid, cardiolipin (CL), as a potential therapeutic target. NARP cybrids harboring 98% of mtDNA T8993G genes and its parental osteosarcoma 143B cells were studied for comparison, and protection provided by melatonin, a potent mitochondrial protector, was explored. We demonstrate for the first time that NARP mutation significantly enhances apoptotic death as a result of three distinct lethal mitochondrial apoptotic insults including oxidative, Ca(2+), and lipid stress. In addition, NARP significantly augmented pathological depletion of CL. NARP-augmented depletion of CL results in enhanced retardation of mitochondrial movement and fission and later swelling of mitochondria during all insults. These results suggest that CL is a common and crucial pathological target for mitochondrial apoptotic insults. Furthermore, CL possibly plays a central role in regulating mitochondrial dynamics that are associated with NARP-augmented mitochondrial pathologies. Intriguingly, melatonin, by differentially preserving CL during various stresses (oxidation > Ca(2+) > lipid), rescues differentially CL-altered mitochondrial dynamics and cell death (oxidation > Ca(2+) > lipid). Thus, melatonin, in addition to being a mitochondrial antioxidant to antagonize mitochondrial oxidative stress, a mitochondrial permeability transition modulator to antagonize mitochondrial Ca(2+) stress, may stabilize directly CL to prevent its oxidization and/or depletion and, therefore, exerts great potential in rescuing CL-dependent mitochondrial dynamics-associated mitochondrial pathologies for treatment of NARP-induced pathologies and diseases.