Rhinoviral infections activate p38MAP-kinases via membrane rafts and RhoA.

Rhinoviral infections belong to the most frequent human infections characterized by common cold, chronic bronchitis, exacerbations of asthma, otitis media and sinusitis. Here, we define molecular mechanisms that mediate infections of human epithelial cells with human rhinovirus strain 14 (RV14). We demonstrate that RV14 activates p38-MAPKinase (p38-K) in a biphasic time course. Early stimulation of p38-K by RV14 was observed a few minutes after initiation of the infection, while the late increase of p38-K activity occurred 7-12 hrs upon infection. The stimulation of p38-K was mediated by the small G-protein RhoA,which was activated by RV14. Transfection of a genetic construct preventing RhoA activation blocked RV14-induced p38-K activation. Further, integrity of cholesterol and sphingolipid-enriched membrane domains was required for RV14-mediated p38-K activation, which was inhibited by destruction of membrane rafts. The data indicate that RV employs a signaling cascade from membrane rafts via the small G-protein RhoA to p38-K to infect human cells.     

The c-jun kinase/stress-activated pathway: regulation, function and role in human disease

c-Jun N-terminal kinases (JNKs), also referred to as stress-activated kinases (SAPKs), were initially characterized by their activation in response to cell stress such as UV irradiation. JNK/SAPKs have since been characterized to be involved in proliferation, apoptosis, motility, metabolism and DNA repair. Dysregulated JNK signaling is now believed to contribute to many diseases involving neurodegeneration, chronic inflammation, birth defects, cancer and ischemia/reperfusion injury. In this review, we present our current understanding of JNK regulation and their involvement in homeostasis and dysregulation in human disease.     

The p38 signal transduction pathway: activation and function

The p38 signalling transduction pathway, a Mitogen-activated protein (MAP) kinase pathway, plays an essential role in regulating many cellular processes including inflammation, cell differentiation, cell growth and death. Activation of p38 often through extracellular stimuli such as bacterial pathogens and cytokines, mediates signal transduction into the nucleus to turn on the responsive genes. p38 also transduces signals to other cellular components to execute different cellular responses. In this review, we summarize the characteristics of the major components of the p38 signalling transduction pathway and highlight the targets of this pathway and the physiological function of the p38 activation.     

A specific mechanomodulatory role for p38 MAPK in embryonic joint articular surface cell MEK-ERK pathway regulation

Mechanisms regulating cell behavior and extracellular matrix composition in response to mechanical stimuli remain unresolved. Our previous studies have established that the MEK-ERK cascade plays a specific role in the mechano-dependent joint formation process by promoting the assembly of pericellular matrices reliant upon hyaluronan (HA) for their integrity. Here we demonstrate: (i) novel cross-talk between p38 MAPK and MEK-ERK signaling pathways that is specific for mechanical stimuli and (ii) a role for p38 MAPK in facilitating HA production by cells derived from the articular surface of embryonic chick tibiotarsal joints. We find that p38 MAPK blockade restricts pericellular assembly of HA-rich matrices and reduces basal as well as mechanical strain-induced release of HA. p38 MAPK blockers potentiated early strain-induced increases but restricted sustained increases in MEK/ERK phosphorylation at later times; c-Fos hyperphosphorylation at threonine 325 was found to parallel this p38 MAPK-mediated modulation of ERK activation. In contrast, p38 MAPK inhibitors had no detectable effect on the ERK activation induced by fibroblast growth factor 2 or pervanadate, a phosphatase inhibitor, and MEK inhibitors did not influence p38 MAPK phosphorylation, confirming both the specificity and unidirectionality of p38 MAPK-ERK cross-talk. Immunochemical and immunoblotting studies revealed constitutive p38 MAPK activation in cells at, or derived from, developing articular joint surfaces. Unlike the MEK-ERK pathway, however, p38 MAPK was not further stimulated by mechanical stimulation in vitro. Thus, p38 MAPK specifically facilitates ERK activation and downstream signaling in response to mechanical stimuli. These results suggest that constitutively active p38 MAPK serves an essential, permissive role in mechanically induced changes in ERK activation and in the accumulation of HA-rich extracellular matrices that serve a key role in joint development.     

封闭蛋白的结构、功能及其与人类疾病

紧密连接（tight junction,TJ）是脊椎动物细胞间连接的一种主要形式,对介导上皮细胞间的黏合、维持上皮细胞的功能具有重要作用。TJ是由一系列跨膜蛋白和外周蛋白相互作用而形成的一个复杂的蛋白质体系,封闭蛋白（occludin）是构成TJ的主要成分之一。目前,已发现封闭蛋白与许多人类疾病有关。本文仅就封闭蛋白的结构、功能及其与人类疾病的关系做一综述。     

Raf kinases: function, regulation and role in human cancer

The Ras-Raf-MAPK pathway regulates diverse physiological processes by transmitting signals from membrane based receptors to various nuclear, cytoplasmic and membrane-bound targets, coordinating a large variety of cellular responses. Function of Raf family kinases has been shown to play a role during organism development, cell cycle regulation, cell proliferation and differentiation, cell survival and apoptosis and many other cellular and physiological processes. Aberrations along the Ras-Raf-MAPK pathway play an integral role in various biological processes concerning human health and disease. Overexpression or activation of the pathway components is a common indicator in proliferative diseases such as cancer and contributes to tumor initiation, progression and metastasis. In this review, we focus on the physiological roles of Raf kinases in normal and disease conditions, specifically cancer, and the current thoughts on Raf regulation.     

The mTOR pathway and its role in human genetic diseases

The signalling components upstream and downstream of the protein kinase mammalian target of rapamycin (mTOR) are frequently altered in a wide variety of human diseases. Upstream of mTOR key signalling molecules are the small GTPase Ras, the lipid kinase PI3K, the Akt kinase, and the GTPase Rheb, which are known to be deregulated in many human cancers. Mutations in the mTOR pathway component genes TSC1, TSC2, LKB1, PTEN, VHL, NF1 and PKD1 trigger the development of the syndromes tuberous sclerosis, Peutz-Jeghers syndrome, Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, Lhermitte-Duclos disease, Proteus syndrome, von Hippel-Lindau disease, Neurofibromatosis type 1, and Polycystic kidney disease, respectively. In addition, the tuberous sclerosis proteins have been implicated in the development of several sporadic tumors and in the control of the cyclin-dependent kinase inhibitor p27, known to be of relevance for several cancers. Recently, it has been recognized that mTOR is regulated by TNF-alpha and Wnt, both of which have been shown to play critical roles in the development of many human neoplasias. In addition to all these human diseases, the role of mTOR in Alzheimer's disease, cardiac hypertrophy, obesity and type 2 diabetes is discussed.     

miR-34a expression,epigenetic regulation,and function in human placental diseases

Preeclampsia (PE) is the major pregnancy-induced hypertensive disorder responsible for maternal and fetal morbidity and mortality that can be associated with intrauterine growth restriction (IUGR). PE and IUGR are thought to be due to a placental defect, occurring early during pregnancy. Several placental microRNAs (miRNAs) have been shown to be deregulated in the context of placental diseases and could thus play a role in the pathophysiology of PE. Here, we show that pri-miR-34a is overexpressed in preeclamptic placentas and that its placental expression is much higher during the first trimester of pregnancy than at term, suggesting a possible developmental role. We explored pri-miR-34a regulation and showed that P53, a known activator of miR-34a, is reduced in all pathological placentas and that hypoxia can induce pri-miR-34a expression in JEG-3 cells. We also studied the methylation status of the miR-34a promoter and revealed hypomethylation in all preeclamptic placentas (associated or not with IUGR), whereas hypoxia induced a hypermethylation in JEG-3 cells at 72 h. Despite the overexpression of pri-miR-34a in preeclampsia, there was a striking decrease of the mature miR-34a in this condition, suggesting preeclampsia-driven alteration of pri-miR-34a maturation. SERPINA3, a protease inhibitor involved in placental diseases, is elevated in IUGR and PE. We show here that miR-34a overexpression in JEG-3 downregulates SERPINA3. The low level of mature miR-34a could thus be an important mechanism contributing to SERPINA3 upregulation in placental diseases. Overall, our results support a role for miR-34a in the pathophysiology of preeclampsia, through deregulation of the pri-miRNA expression and its altered maturation.     

Mitochondrial regulation of epigenetics and its role in human diseases

Most pathogenic mitochondrial DNA (mtDNA) mutations induce defects in mitochondrial oxidative phosphorylation (OXPHOS). However, phenotypic effects of these mutations show a large degree of variation depending on the tissue affected. These differences are difficult to reconcile with OXPHOS as the sole pathogenic factor suggesting that additional mechanisms contribute to lack of genotype and clinical phenotype correlationship. An increasing number of studies have identified a possible effect on the epigenetic landscape of the nuclear genome as a consequence of mitochondrial dysfunction. In particular, these studies demonstrate reversible or irreversible changes in genomic DNA methylation profiles of the nuclear genome. Here we review how mitochondria damage checkpoint (mitocheckpoint) induces epigenetic changes in the nucleus. Persistent pathogenic mutations in mtDNA may also lead to epigenetic changes causing genomic instability in the nuclear genome. We propose that “mitocheckpoint” mediated epigenetic and genetic changes may play key roles in phenotypic variation related to mitochondrial diseases or host of human diseases in which mitochondrial defect plays a primary role.     

Mitochondrial regulation of epigenetics and its role in human diseases

Most pathogenic mitochondrial DNA (mtDNA) mutations induce defects in mitochondrial oxidative phosphorylation (OXPHOS). However, phenotypic effects of these mutations show a large degree of variation depending on the tissue affected. These differences are difficult to reconcile with OXPHOS as the sole pathogenic factor suggesting that additional mechanisms contribute to lack of genotype and clinical phenotype correlationship. An increasing number of studies have identified a possible effect on the epigenetic landscape of the nuclear genome as a consequence of mitochondrial dysfunction. In particular, these studies demonstrate reversible or irreversible changes in genomic DNA methylation profiles of the nuclear genome. Here we review how mitochondria damage checkpoint (mitocheckpoint) induces epigenetic changes in the nucleus. Persistent pathogenic mutations in mtDNA may also lead to epigenetic changes causing genomic instability in the nuclear genome. We propose that “mitocheckpoint” mediated epigenetic and genetic changes may play key roles in phenotypic variation related to mitochondrial diseases or host of human diseases in which mitochondrial defect plays a primary role.     

Differential role of the JNK and p38 MAPK pathway in c-Myc- and s-Myc-mediated apoptosis

The s-Myc is similar to c-Myc in its ability to induce apoptosis requiring caspase activation. However, s-Myc is distinct from c-Myc in that it has activity to suppress tumor growth and does not require wild-type p53 to induce apoptosis. These facts suggest differential regulation between s-Myc and c-Myc. Here we showed that s-Myc-mediated apoptosis triggered by UV was not inhibited by the inactive form mutant JNK (APF), though c-Myc-mediated apoptosis was. Moreover, we found that JNK did not affect the transactivation activity of s-Myc, but stimulated that of c-Myc. In contrast, both Myc-mediated apoptosis and caspase-3-like protease activation were suppressed by kinase-negative MKK6 and an inactive form mutant p38(AGF). Our results indicate that s-Myc does not require the JNK signaling unlike c-Myc during UV-triggered apoptosis, but the MKK6/p38MAPK pathway might regulate common apoptotic machinery for both s-Myc and c-Myc upstream of caspase.     

p38 MAPKs在细胞周期调控中的作用

p38丝裂原活化蛋白激酶(mitogen-activated protein kinases,MAPKs)作为MAPK家族的成员,传统认为它主要参与调控细胞应激反应和免疫反应。近年来发现它还参与调控细胞的增殖、凋亡和分化。在不同应激刺激下,p38 MAPKs通过多条信号转导通路作用于细胞周期的各个检验点,抑制细胞增殖,阻滞细胞于不同周期。     

p38 MAPK信号传导通路

丝裂原活化蛋白激酶（ｍｉｔｏｇｅｎ－ａｃｔｉｖａｔｅｄｐｏｒｏｔｅｉｎｋｉｎａｓｅ,ＭＡＰＫ）介导了生长、发育,分裂,死亡,以及细胞间的功能同步等多种细胞生理功能,在哺乳动物细胞中已发现和克隆了ＥＲＫ、ＪＮＫ／ＳＡＰＫ,ＥＲＫ５／ＢＭＫ１和ｐ３８／ＲＫ四个ＭＡＰＫ亚族,这些新的ＭＡＰＫ介导了物理,化学反激,细菌产物,炎性细胞因子等多种刺激引起的细胞反应,ｐ３８亚族至少包括ｐ３８（α）,ｐ３８β,ｐ     

A role for protein phosphatase-2A in p38 mitogen-activated protein kinase-mediated regulation of the c-Jun NH(2)-terminal kinase pathway in human neutrophils

Human neutrophil accumulation in inflammatory foci is essential for the effective control of microbial infections. Although exposure of neutrophils to cytokines such as tumor necrosis factor-alpha (TNFalpha), generated at sites of inflammation, leads to activation of MAPK pathways, mechanisms responsible for the fine regulation of specific MAPK modules remain unknown. We have previously demonstrated activation of a TNFalpha-mediated JNK pathway module, leading to apoptosis in adherent human neutrophils (Avdi, N. J., Nick, J. A., Whitlock, B. B., Billstrom, M. A., Henson, P. M., Johnson, G. L., and Worthen, G. S. (2001) J. Biol. Chem. 276, 2189-2199). Herein, evidence is presented linking regulation of the JNK pathway to p38 MAPK and the Ser/Thr protein phosphatase-2A (PP2A). Inhibition of p38 MAPK by SB 203580 and M 39 resulted in significant augmentation of TNFalpha-induced JNK and MKK4 (but not MKK7 or MEKK1) activation, whereas prior exposure to a p38-activating agent (platelet-activating factor) diminished the TNFalpha-induced JNK response. TNFalpha-induced apoptosis was also greatly enhanced upon p38 inhibition. Studies with a reconstituted cell-free system indicated the absence of a direct inhibitory effect of p38 MAPK on the JNK module. Neutrophil exposure to the Ser/Thr phosphatase inhibitors okadaic acid and calyculin A induced JNK activation. Increased phosphatase activity following TNFalpha stimulation was shown to be PP2A-associated and p38-dependent. Furthermore, PP2A-induced dephosphorylation of MKK4 resulted in its inactivation. Thus, in neutrophils, p38 MAPK, through a PP2A-mediated mechanism, regulates the JNK pathway, thus determining the extent and nature of subsequent responses such as apoptosis.     

Activation and expression of ERK, JNK, and p38 MAP-kinases in isolated islets of Langerhans: implications for cultured islet survival.

Isolation and purification of islet cells exposes them to ischemic, osmotic and mechanical stresses. The objective of this study was to determine the roles of the MAP-kinases in islets immediately following isolation. During the first 48 h, activity of JNK1 and JNK2 declined markedly. Activity of p38 increased steadily with time in culture while extracellular signal regulated kinase (ERK) activity declined dramatically within 24 h post-isolation. High p38 activation relative to ERK activation immediately following isolation correlated with a decrease in islet survival after 36 h in culture. Absence and/or transiency of ERK signaling in conjunction with sustained activation of p38 pathway could be an important regulator of cell death in islets during and following their isolation by commonly employed procedures.     

The regulation of human reproduction by p53 and its pathway

Comment on: Kang HJ, et al. Proc Natl Acad Sci U S A 2009; 106:9761-6.     

p38MAPK信号通路与肺纤维化

肺纤维化(Pulmonary fibrosis,PF)是一种进行性发展的、破坏性的纤维化疾病,其主要特征为肺泡上皮细胞损伤、炎性细胞浸润、上皮间充质转变、成纤维细胞的异常增殖和活化、细胞外基质的过度沉积,最终导致肺实质性的破坏。其具体机制不明,目前缺乏有效的治疗手段逆转这种疾病或阻止其发展。近年来的研究发现,信号传导通路在肺纤维化形成过程中的作用越来越受到关注,其中p38丝裂原活化蛋白激酶(p38mitogen-activated protein kinase,p38MAPK)信号通路通过介导炎性细胞浸润、成纤维细胞增殖等参与PF的形成过程。本文就p38MAPK在PF形成过程中的作用作一综述。     

The regulation of p53, p38 MAPK,JNK and XBP-1s by sphingosine kinases in human embryonic kidney cells

Since inhibitors of sphingosine kinases (SK1, SK2) have been shown to induce p53-mediated cell death, we have further investigated their role in regulating p53, stress activated protein kinases and XBP-1s in HEK293T cells. Treatment of these cells with the sphingosine kinase inhibitor, SKi, which fails to induce apoptosis, promoted the conversion of p53 into two proteins with molecular masses of 63 and 90 kDa, and which was enhanced by over-expression of ubiquitin. The SKi induced conversion of p53 to p63/p90 was also enhanced by siRNA knockdown of SK1, but not SK2 or dihydroceramide desaturase (Degs1), suggesting that SK1 is a negative regulator of this process. In contrast, another sphingosine kinase inhibitor, ABC294640 only very weakly stimulated formation of p63/p90 and induced apoptosis of HEK293T cells. We have previously shown that SKi promotes the polyubiquitination of Degs1, and these forms positively regulate p38 MAPK/JNK pathways to promote HEK293T cell survival/growth. siRNA knockdown of SK1 enhanced the activation of p38 MAPK/JNK pathways in response to SKi, suggesting that SK1 functions to oppose these pro-survival pathways in HEK293T cells. SKi also enhanced the stimulatory effect of the proteasome inhibitor, MG132 on the expression of the pro-survival protein XBP-1s and this was reduced by siRNA knockdown of SK2 and increased by knockdown of p53. These findings suggest that SK1 and SK2 have opposing roles in regulating p53-dependent function in HEK293T cells.