The Akt proto-oncogene links Ras to Pak and cell survival signals

ROS production by mitochondria: function or dysfunction?

In eukaryotic cells, ATP generation is generally viewed as the primary function of mitochondria under normoxic conditions. Reactive oxygen species (ROS), in contrast, are regarded as the by-products of respiration, and are widely associated with dysfunction and disease. Important signaling functions have been demonstrated for mitochondrial ROS in recent years. Still, their chemical reactivity and capacity to elicit oxidative damage have reinforced the idea that ROS are the products of dysfunctional mitochondria that accumulate during disease. Several studies support a different model, however, by showing that: (1) limited oxygen availability results in mitochondria prioritizing ROS production over ATP, (2) ROS is an essential adaptive mitochondrial signal triggered by various important stressors, and (3) while mitochondria-independent ATP production can be easily engaged by most cells, there is no known replacement for ROS-driven redox signaling. Based on these observations and other evidence reviewed here, we highlight the role of ROS production as a major mitochondrial function involved in cellular adaptation and stress resistance. As such, we propose a rekindled view of ROS production as a primary mitochondrial function as essential to life as ATP production itself.

YB-1 activating cascades as potential targets in KRAS-mutated tumors

Y‑box binding protein‑1 (YB-1) is a multifunctional protein that is highly expressed in human solid tumors of various entities. Several cellular processes, e.g. cell cycle progression, cancer stemness and DNA damage signaling that are involved in the response to chemoradiotherapy (CRT) are tightly governed by YB‑1. KRAS gene with about 30% mutations in all cancers, is considered the most commonly mutated oncogene in human cancers. Accumulating evidence indicates that oncogenic KRAS mediates CRT resistance. AKT and p90 ribosomal S6 kinase are downstream of KRAS and are the major kinases that stimulate YB‑1 phosphorylation. Thus, there is a close link between the KRAS mutation status and YB‑1 activity. In this review paper, we highlight the importance of the KRAS/YB‑1 cascade in the response of KRAS-mutated solid tumors to CRT. Likewise, the opportunities to interfere with this pathway to improve CRT outcome are discussed in light of the current literature.

Pathophysiological impact of CXC and CX3CL1 chemokines in preeclampsia and gestational diabetes mellitus

Diabetes-related pathophysiological alterations and various female reproductive difficulties were common in pregnant women with gestational diabetes mellitus (GDM), who had 21.1 million live births. Preeclampsia (PE), which increases maternal and fetal morbidity and mortality, affects approximately 3%-5% of pregnancies worldwide. Nevertheless, it is unclear what triggers PE and GDM to develop. Therefore, the development of novel moderator therapy approaches is a crucial advancement. Chemokines regulate physiological defenses and maternal-fetal interaction during healthy and disturbed pregnancies. Chemokines regulate immunity, stem cell trafficking, anti-angiogenesis, and cell attraction. CXC chemokines are usually inflammatory and contribute to numerous reproductive disorders. Fractalkine (CX3CL1) may be membrane-bound or soluble. CX3CL1 aids cell survival during homeostasis and inflammation. Evidence reveals that CXC and CX3CL1 chemokines and their receptors have been the focus of therapeutic discoveries for clinical intervention due to their considerable participation in numerous biological processes. This review aims to give an overview of the functions of CXC and CX3CL1 chemokines and their receptors in the pathophysiology of PE and GDM. Finally, we examined stimulus specificity for CXC and CX3CL1 chemokine expression and synthesis in PE and GDM and preclinical and clinical trials of CXC-based PE and GDM therapies.

PAK1 and Therapy Resistance in Melanoma

Malignant melanoma claims more lives than any other skin malignancy. While primary melanomas are usually cured via surgical excision, the metastatic form of the disease portents a poor prognosis. Decades of intense research has yielded an extensive armamentarium of anti-melanoma therapies, ranging from genotoxic chemo- and radiotherapies to targeted interventions in specific signaling pathways and immune functions. Unfortunately, even the most up-to-date embodiments of these therapies are not curative for the majority of metastatic melanoma patients, and the need to improve their efficacy is widely recognized. Here, we review the reports that implicate p21-regulated kinase 1 (PAK1) and PAK1-related pathways in the response of melanoma to various therapeutic modalities. Ample data suggest that PAK1 may decrease cell sensitivity to programmed cell death, provide additional stimulation to growth-promoting molecular pathways, and contribute to the creation of an immunosuppressive tumor microenvironment. Accordingly, there is mounting evidence that the concomitant inhibition of PAK1 enhances the potency of various anti-melanoma regimens. Overall, the available information suggests that a safe and effective inhibition of PAK1-dependent molecular processes would enhance the potency of the currently available anti-melanoma treatments, although considerable challenges in implementing such strategies still exist.

Farnesyl diphosphate synthase regulated endothelial proliferation and autophagy during rat pulmonary arterial hypertension induced by monocrotaline

Background

The proliferation ability and autophagy level of pulmonary artery endothelial cells (PAECs) play an important role in promoting the development of pulmonary artery hypertension (PAH), and there is still no effective treatment for PAH. Farnesyl diphosphate synthase (FDPS) is a key enzyme in the mevalonate pathway. The intermediate metabolites of this pathway are closely related to the activity of autophagy-associated small G proteins, including Ras-related C3 botulinum toxin substrate 1 (Rac1). Studies have shown that the mevalonate pathway affects the activation levels of different small G proteins, autophagy signaling pathways, vascular endothelial function, and so on. However, the exact relationship between them is still unclear in PAH.

Method

In vitro, western blotting and mRFP-GFP-LC3 puncta formation assays were used to observe the expression of FDPS and the level of autophagy in PAECs treated with monocrotaline pyrrole (MCTP). In addition, cell proliferation and migration assays were used to assess the effect of FDPS on endothelial function, and Rac1 activity assays were used to evaluate the effect of Rac1 activation on PAEC autophagy via the PI3K/AKT/mTOR signaling pathway. In vivo, the right heart catheterization method, hematoxylin and eosin (H&E) staining and western blotting were used to determine the effect of FDPS on PAEC autophagy and monocrotaline (MCT)-induced PAH.

Results

We show that the expression of FDPS is increased in the PAH module in vitro and in vivo, concomitant with the induction of autophagy and the activation of Rac1. Our data demonstrate that inhibition of FDPS ameliorates endothelial function and decreases MCT-induced autophagy levels. Mechanistically, we found that FDPS promotes autophagy, Rac1 activity and endothelial disfunction through the PI3K/AKT/mTOR signaling pathway.

Conclusion

Our study suggests that FDPS contributes to active small G protein-induced autophagy during MCT-induced PAH, which may serve as a potential therapeutic target against PAH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00511-7.

Chemokines in Gestational Diabetes Mellitus

Background

Studies investigating chemokines in gestational diabetes mellitus (GDM) have yielded mixed results. The purpose of this meta-analysis was to explore whether concentrations of chemokines in patients with GDM differed from that of the controls.

Methods

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically searched Web of Science, Embase, Cochrane Library, and PubMed databases for articles, published in any language, on chemokines and GDM through August 1st, 2021. The difference in concentrations of chemokines between patients with GDM and controls was determined by a standardized mean difference (SMD) with a 95% confidence interval (CI), calculated in the meta-analysis of the eligible studies using a random-effects model with restricted maximum-likelihood estimator.

Results

Seventeen studies met the inclusion criteria for the meta-analysis. Altogether, they included nine different chemokines comparisons involving 5,158 participants (1,934 GDM patients and 3,224 controls). Results showed a significant increase of these chemokines (CCL2, CXCL1, CXCL8, CXCL9, and CXCL12) in the GDM patients compared with the controls. However, there was a significant decrease of the chemokines, CCL4, CCL11 and CXCL10, in the GDM patients compared with the controls. Moreover, subgroup analysis revealed a potential role of chemokines as biomarkers in relation to laboratory detection (different sample type and assay methods) and clinical characteristics of GDM patients (ethnicity and body mass index).

Conclusion

GDM is associated with several chemokines (CCL2, CCL4, CCL11, CXCL1, CXCL8, CXCL9, CXCL10 and CXCL12). Therefore, consideration of these chemokines as potential targets or biomarkers in the pathophysiology of GDM development is necessary. Notably, the information of subgroup analysis underscores the importance of exploring putative mechanisms underlying this association, in order to develop new individualized clinical and therapeutic strategies.

Group I PAKs in myelin formation and repair of the central nervous system: what, when, and how

p21-activated kinases (PAKs) are a family of cell division control protein 42/ras-related C3 botulinum toxin substrate 1 (Cdc42/Rac1)-activated serine/threonine kinases. Group I PAKs (PAK1-3) have distinct activation mechanisms from group II PAKs (PAK4-6) and are the focus of this review. In transformed cancer cells, PAKs regulate a variety of cellular processes and molecular pathways which are also important for myelin formation and repair in the central nervous system (CNS). De novo mutations in group I PAKs are frequently seen in children with neurodevelopmental defects and white matter anomalies. Group I PAKs regulate virtually every aspect of neuronal development and function. Yet their functions in CNS myelination and remyelination remain incompletely defined. Herein, we highlight the current understanding of PAKs in regulating cellular and molecular pathways and discuss the status of PAK-regulated pathways in oligodendrocyte development. We point out outstanding questions and future directions in the research field of group I PAKs and oligodendrocyte development.

Pak1 kinase controls cell shape through ribonucleoprotein granules

Fission yeast cells maintain a rod shape due to conserved signaling pathways that organize the cytoskeleton for polarized growth. We discovered a mechanism linking the conserved protein kinase Pak1 with cell shape through the RNA-binding protein Sts5. Pak1 (also called Shk1 and Orb2) prevents Sts5 association with P bodies by directly phosphorylating its intrinsically disordered region (IDR). Pak1 and the cell polarity kinase Orb6 both phosphorylate the Sts5 IDR but at distinct residues. Mutations preventing phosphorylation in the Sts5 IDR cause increased P body formation and defects in cell shape and polarity. Unexpectedly, when cells encounter glucose starvation, PKA signaling triggers Pak1 recruitment to stress granules with Sts5. Through retargeting experiments, we reveal that Pak1 localizes to stress granules to promote rapid dissolution of Sts5 upon glucose addition. Our work reveals a new role for Pak1 in regulating cell shape through ribonucleoprotein granules during normal and stressed growth conditions.

Chemokines in Prediabetes and Type 2 Diabetes: A Meta-Analysis

Background

A growing number of studies found inconsistent results on the role of chemokines in the progression of type 2 diabetes (T2DM) and prediabetes (PDM). The purpose of this meta-analysis was to summarize the results of previous studies on the association between the chemokines system and T2DM/PDM.

Methods

We searched in the databases, PubMed, Web of Science, Embase and Cochrane Library, for eligible studies published not later than March 1, 2020. Data extraction was performed independently by 2 reviewers, on a standardized, prepiloted form. Group differences in chemokines concentrations were summarized using the standardized mean difference (SMD) with a 95% confidence interval (CI), calculated by performing a meta-analysis using the random-effects model.

Results

We identified 98 relevant studies that investigated the association between 32 different chemokines and T2DM/PDM. Altogether, these studies involved 14,708 patients and 14,574 controls. Results showed that the concentrations of CCL1, CCL2, CCL4, CCL5, CCL11, CXCL8, CXCL10 and CX3CL1 in the T2DM patients were significantly higher than that in the controls, while no difference in these concentrations was found between the PDM patients and controls.

Conclusion

Progression of T2DM may be associated with elevated concentrations of chemokines.

Meta-Analysis Registration

PROSPERO, identifier CRD42019148305.

PAK1 Positively Regulates Oligodendrocyte Morphology and Myelination

The actin cytoskeleton is crucial for oligodendrocyte differentiation and myelination. Here we show that p21-activated kinase 1 (PAK1), a well-known actin regulator, promotes oligodendrocyte morphologic change and myelin production in the CNS. A combination of in vitro and in vivo models demonstrated that PAK1 is expressed throughout the oligodendrocyte lineage with highest expression in differentiated oligodendrocytes. Inhibiting PAK1 early in oligodendrocyte development decreased oligodendrocyte morphologic complexity and altered F-actin spreading at the tips of oligodendrocyte progenitor cell processes. Constitutively activating AKT in oligodendrocytes in male and female mice, which leads to excessive myelin wrapping, increased PAK1 expression, suggesting an impact of PAK1 during active myelin wrapping. Furthermore, constitutively activating PAK1 in oligodendrocytes in zebrafish led to an increase in myelin internode length while inhibiting PAK1 during active myelination decreased internode length. As myelin parameters influence conduction velocity, these data suggest that PAK1 may influence communication within the CNS. These data support a model in which PAK1 is a positive regulator of CNS myelination.SIGNIFICANCE STATEMENT Myelin is a critical component of the CNS that provides metabolic support to neurons and also facilitates communication between cells in the CNS. Recent data demonstrate that actin dynamics drives myelin wrapping, but how actin is regulated during myelin wrapping is unknown. The authors investigate the role of the cytoskeletal modulator PAK1 during differentiation and myelination by oligodendrocytes, the myelinating cells of the CNS. They demonstrate that PAK1 promotes oligodendrocyte differentiation and myelination by modulating the cytoskeleton and thereby internode length, thus playing a critical role in the function of the CNS.

Interrogation of kinase genetic interactions provides a global view of PAK1-mediated signal transduction pathways

Kinases are critical components of intracellular signaling pathways and have been extensively investigated with regard to their roles in cancer. p21-activated kinase-1 (PAK1) is a serine/threonine kinase that has been previously implicated in numerous biological processes, such as cell migration, cell cycle progression, cell motility, invasion, and angiogenesis, in glioma and other cancers. However, the signaling network linked to PAK1 is not fully defined. We previously reported a large-scale yeast genetic interaction screen using toxicity as a readout to identify candidate PAK1 genetic interactions. En masse transformation of the PAK1 gene into 4,653 homozygous diploid Saccharomyces cerevisiae yeast deletion mutants identified ∼400 candidates that suppressed yeast toxicity. Here we selected 19 candidate PAK1 genetic interactions that had human orthologs and were expressed in glioma for further examination in mammalian cells, brain slice cultures, and orthotopic glioma models. RNAi and pharmacological inhibition of potential PAK1 interactors confirmed that DPP4, KIF11, mTOR, PKM2, SGPP1, TTK, and YWHAE regulate PAK1-induced cell migration and revealed the importance of genes related to the mitotic spindle, proteolysis, autophagy, and metabolism in PAK1-mediated glioma cell migration, drug resistance, and proliferation. AKT1 was further identified as a downstream mediator of the PAK1-TTK genetic interaction. Taken together, these data provide a global view of PAK1-mediated signal transduction pathways and point to potential new drug targets for glioma therapy.

Y-27632 Induces Neurite Outgrowth by Activating the NOX1-Mediated AKT and PAK1 Phosphorylation Cascades in PC12 Cells

Y-27632 is known as a selective Rho-associated coiled coil-forming kinase (ROCK) inhibitor. Y-27632 has been shown to induce neurite outgrowth in several neuronal cells. However, the precise molecular mechanisms linking neurite outgrowth to Y-27632 are not completely understood. In this study, we examined the ability of Y-27632 to induce neurite outgrowth in PC12 cells and evaluated the signaling cascade. The effect of Y-27632 on the neurite outgrowth was inhibited by reactive oxygen species (ROS) scavengers such as N-acetyl cysteine (NAC) and trolox. Furthermore, Y-27632-induced neurite outgrowth was not triggered by NADPH oxidase 1 (NOX1) knockdown or diphenyleneiodonium (DPI), a NOX inhibitor. Suppression of the Rho-family GTPase Rac1, which is under the negative control of ROCK, with expression of the dominant negative Rac1 mutant (Rac1N17) prevented Y-27632-induced neurite outgrowth. Moreover, the Rac1 inhibitor NSC23766 prevented Y-27632-induced AKT and p21-activated kinase 1 (PAK1) activation. AKT inhibition with MK2206 suppressed Y-27632-induced PAK1 phosphorylation and neurite outgrowth. In conclusion, our results suggest that Rac1/NOX1-dependent ROS generation and subsequent activation of the AKT/PAK1 cascade contribute to Y-27632-induced neurite outgrowth in PC12 cells.

Effect of Chrysanthemum zawadskii Extract on Dermal Papilla Cell Proliferation and Hair Growth

Background

Chrysanthemum zawadskii (CZ) belongs to the genus Chrysanthemum, also known as ‘Gu-Jeol-Cho’ in Korea. CZ has been used as herbal remedy to manage cough, hypertensive disorders, pharyngitis, bronchitis, gastroenteritis, pneumonia, bladder diseases and common cold. However, its effect on hair growth has not been documented.

Objective

The aim of present study was to elucidate the beneficial effects of CZ on hair growth.

Methods

Proliferation of follicular dermal papilla (DP) cells from human scalp skin was evaluated by MTT assay. The expression of various molecules in DP cells was checked by western blot assay. Effect of CZ extract on the hair growth was evaluated by hair organ culture and C57BL/6 mice model.

Results

Cultivation of DP cells with CZ extract increased cellular proliferation, increased expression of phosphorylated protein kinase B (p-Akt), p-ERK, B-cell lymphoma 2, and decreased expression of Bax. Treatment of human hair follicles with CZ extract significantly enhanced hair growth. Additionally, CZ markedly shortened telogen period, increased anagen transformation and stimulated hair growth in the animal study.

Conclusion

These results suggest that CZ extract has an effect of promoting hair growth and may therefore be a useful a therapeutic remedy for preventing hair loss.

The Actin Cytoskeleton in Myelinating Cells

Myelinating cells of both the peripheral and central nervous systems (CNSs) undergo dramatic cytoskeletal reorganization in order to differentiate and produce myelin. Myelinating oligodendrocytes in the CNS show a periodic actin pattern, demonstrating tight regulation of actin. Furthermore, recent data demonstrate that actin polymerization drives early cell differentiation and that actin depolymerization drives myelin wrapping. Dysregulation of the actin cytoskeleton in myelinating cells is seen in some disease states. This review highlights the cytoskeletal molecules that regulate differentiation of and myelination by cells of the PNS and CNS, informing our understanding of neural development, in particular myelination.

Extracellular Domains I and II of cell-surface glycoprotein CD44 mediate its trans-homophilic dimerization and tumor cluster aggregation

CD44 molecule (CD44) is a well-known surface glycoprotein on tumor-initiating cells or cancer stem cells. However, its utility as a therapeutic target for managing metastases remains to be fully evaluated. We previously demonstrated that CD44 mediates homophilic interactions for circulating tumor cell (CTC) cluster formation, which enhances cancer stemness and metastatic potential in association with an unfavorable prognosis. Furthermore, CD44 self-interactions activate the P21-activated kinase 2 (PAK2) signaling pathway. Here, we further examined the biochemical properties of CD44 in homotypic tumor cell aggregation. The standard CD44 form (CD44s) mainly assembled as intercellular homodimers (trans-dimers) in tumor clusters rather than intracellular dimers (cis-dimers) present in single cells. Machine learning-based computational modeling combined with experimental mutagenesis tests revealed that the extracellular Domains I and II of CD44 are essential for its trans-dimerization and predicted high-score residues to be required for dimerization. Substitutions of 10 these residues in Domain I (Ser-45, Glu-48, Phe-74, Cys-77, Arg-78, Tyr-79, Ile-88, Arg-90, Asn-94, and Cys-97) or 5 residues in Domain II (Ile-106, Tyr-155, Val-156, Gln-157, and Lys-158) abolished CD44 dimerization and reduced tumor cell aggregation in vitro Importantly, the substitutions in Domain II dramatically inhibited lung colonization in mice. The CD44 dimer-disrupting substitutions decreased downstream PAK2 activation without affecting the interaction between CD44 and PAK2, suggesting that PAK2 activation in tumor cell clusters is CD44 trans-dimer-dependent. These results shed critical light on the biochemical mechanisms of CD44-mediated tumor cell cluster formation and may help inform the development of therapeutic strategies to prevent tumor cluster formation and block cluster-mediated metastases.

Post-Treatment with Erinacine A, a Derived Diterpenoid of H. erinaceus, Attenuates Neurotoxicity in MPTP Model of Parkinson's Disease

Hericium erinaceus, a valuable pharmaceutical and edible mushroom, contains potent bioactive compounds such as H. erinaceus mycelium (HEM) and its derived ethanol extraction of erinacine A, which have been found to regulate physiological functions in our previous study. However, HEM or erinacine A with post-treatment regimens also shows effects on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity, but its mechanisms remain unknown. By using annexin-V–fluorescein-isothiocyanate (FITC)/propidium iodide staining and a 2’,7’ –dichlorofluorescin diacetate (DCFDA) staining assay, the cell death, cell viability, and reactive oxygen species (ROS) of 1-methyl-4-phenylpyridinium (MMP⁺)-treated Neuro-2a (N2a) cells with or without erinacine A addition were measured, respectively. Furthermore, signaling molecules for regulating the p21/GADD45 cell death pathways and PAKalpha, p21 (RAC1) activated kinase 1 (PAK1) survival pathways were also detected in the cells treated with MPP⁺ and erinacine A by Western blots. In neurotoxic animal models of MPTP induction, the effects of HEM or erinacine A and its mechanism in vivo were determined by measuring the TH-positive cell numbers and the protein level of the substantia nigra through a brain histological examination. Our results demonstrated that post-treatment with erinacine A was capable of preventing the cytotoxicity of neuronal cells and the production of ROS in vitro and in vivo through the neuroprotective mechanism for erinacine A to rescue the neurotoxicity through the disruption of the IRE1α/TRAF2 interaction and the reduction of p21 and GADD45 expression. In addition, erinacine A treatment activated the conserved signaling pathways for neuronal survival via the phosphorylation of PAK1, AKT, LIM domain kinase 2 (LIMK2), extracellular signal-regulated kinases (ERK), and Cofilin. Similar changes in the signal molecules also were found in the substantia nigra of the MPTP, which caused TH+ neuron damage after being treated with erinacine A in the post-treatment regimens in a dose-dependent manner. Taken together, our data indicated a novel mechanism for post-treatment with erinacine A to protect from neurotoxicity through regulating neuronal survival and cell death pathways.

Norgalanthamine Stimulates Proliferation of Dermal Papilla Cells via Anagen-Activating Signaling Pathways

Norgalanthamine has been shown to possess hair-growth promoting effects, including increase in hair-fiber length in cultured rat vibrissa follicles and increase in dermal papilla cell (DPC) proliferation. However, the intracellular mechanisms that underlie the action of norgalanthamine in DPCs have not been investigated. In this study, we addressed the ability of norgalanthamine to trigger anagen-activating signaling pathways in DPCs. Norgalanthamine significantly increased extracellular signal-regulated kinase (ERK) 1/2 phosphorylation at 0.1 µM, a concentration at which DPC proliferation was also induced. Furthermore, the increases in norgalanthamine-induced ERK 1/2 activation and subsequent DPC proliferation were suppressed by the mitogen-activated protein kinase/ERK kinase (MEK) 1/2 inhibitor, U0126. A 0.1 µM dose of norgalanthamine also increased phosphorylation of AKT, which was followed by an increase in glycogen synthase kinase 3β phosphorylation and nuclear translocation of β-catenin. In addition, LY294002, a phosphatidylinositol 3 kinase (PI3K) inhibitor, blocked the effect of norgalanthamine on DPC proliferation. These results suggest that norgalanthamine can stimulate the anagen phase of the hair cycle in DPCs via activation of the ERK 1/2, PI3K/AKT, and Wnt/β-catenin pathways.

Correlation between microsatellite instability and RAS gene mutation and stage III colorectal cancer

Correlation between RAS gene mutation and microsatellite instability (MSI) status in cancer tissues and clinicopathological parameters of patients with stage III colorectal cancer (CRC) were investigated. Tissues were collected from 180 patients diagnosed with stage III CRC in the Department of Gastrointestinal Surgery of the Fourth Hospital of Hebei Medical University from 2012 to 2016. RAS gene mutations in paraffin sections were detected by PCR and Sanger sequencing. Expression of mismatch repair proteins MLH1, MSH2, MSH6 and PMS2 was detected by immunohistochemistry, and MSI status was determined based on the positive and negative expression combinations of the above proteins, and the correlation with clinicopathological parameters of CRC was analyzed. Mutation rates of KRAS and NRAS were 48.33% (87/180) and 2.78% (5/180), respectively. Mutation rate of p.G12D in codon 12 of exon 2 in KRAS gene was the highest (31/87, 35.63%). Mutation rate of p.G12D in codon 12 of exon 2 in NRAS gene was the highest (2/5, 40%). Mutation rate of KRAS gene in right colon was higher than that in left colon and rectum (p<0.05), and mutation rate in N2b phase was higher than that in N2a and N1 phases (p<0.01). In low degree of microsatellite instability (MSI-L) and high degree of microsatellite instability (MSI-H) status, negative MKH1 protein expression was dominant (18/32, 56.25%). MSI-H in CRC patients aged ≥50 years was higher than that of CRC patients <50 years. Rates of MSI-H in N1, N2a, and N2b were 1.75, 12.82, and 1.11% (p<0.05). Mutation rate of KRAS gene in MSI-H status of stage III CRC patients was significantly higher than that in MSI-L/microsatellite stability (MSS) (p<0.05). Mutation of RAS gene and the status of MSI are involved in the occurrence and development of stage III CRC. Detection of RAS gene has important significance for the individual treatment of CRC in clinic.

Pseudomonas aeruginosa ExoS Induces Intrinsic Apoptosis in Target Host Cells in a Manner That is Dependent on its GAP Domain Activity

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes serious infections in immunocompromised individuals and cystic fibrosis patients. ExoS and ExoT are two homologous bifunctional Type III Secretion System (T3SS) virulence factors that induce apoptosis in target host cells. They possess a GTPase Activating Protein (GAP) domain at their N-termini, which share ~76% homology, and an ADP-ribosyltransferase (ADPRT) domain at their C-termini, which target non-overlapping substrates. Both the GAP and the ADPRT domains contribute to ExoT's cytotoxicity in target epithelial cells, whereas, ExoS-induced apoptosis is reported to be primarily due to its ADPRT domain. In this report, we demonstrate that ExoS/GAP domain is both necessary and sufficient to induce mitochondrial apoptosis. Our data demonstrate that intoxication with ExoS/GAP domain leads to enrichment of Bax and Bim into the mitochondrial outer-membrane, disruption of mitochondrial membrane and release of and cytochrome c into the cytosol, which activates initiator caspase-9 and effector caspase-3, that executes cellular death. We posit that the contribution of the GAP domain in ExoS-induced apoptosis was overlooked in prior studies due to its slower kinetics of cytotoxicity as compared to ADPRT. Our data clarify the field and reveal a novel virulence function for ExoS/GAP as an inducer of apoptosis.

Deciphering the link between PI3K and PAK: An opportunity to target key pathways in pancreatic cancer?

The development of personalised therapies has ushered in a new and exciting era of cancer treatment for a variety of solid malignancies. Yet pancreatic ductal adenocarcinoma (PDAC) has failed to benefit from this paradigm shift, remaining notoriously refractory to targeted therapies. Chemotherapy is the cornerstone of management but can offer only modest survival benefits of a few months with 5-year survival rates rarely exceeding 3%. Despite these disappointing statistics, significant strides have been made towards understanding the complex biology of pancreatic cancer, with deep genomic sequencing identifying novel genetic aberrations and key signalling pathways. The PI3K-PDK1-AKT pathway has received great attention due to its prominence in carcinogenesis. However, efforts to target several components of this network have resulted in only a handful of drugs demonstrating any survival benefit in solid tumors; despite promising pre-clinical results. p-21 activated kinase 4 (PAK4) is a gene that is recurrently amplified or overexpressed in PDAC and both PAK4 and related family member PAK1, have been linked to aberrant RAS activity, a common feature in pancreatic cancer. As regulators of PI3K, PAKs have been highlighted as a potential prognostic marker and therapeutic target. In this review, we discuss the biology of pancreatic cancer and the close interaction between PAKs and the PI3K pathway. We also suggest proposals for future research that may see the development of effective targeted therapies that could finally improve outcomes for this disease.

P21-activated kinase 1 regulates resistance to BRAF inhibition in human cancer cells

BRAF is a commonly mutated oncogene in various human malignancies and a target of a new class of anti-cancer agents, BRAF-inhibitors (BRAFi). The initial enthusiasm for these agents, based on the early successes in the management of metastatic melanoma, is now challenged by the mounting evidence of intrinsic BRAFi-insensitivity in many BRAF-mutated tumors, by the scarcity of complete responses, and by the inevitable emergence of drug resistance in initially responsive cases. These setbacks put an emphasis on discovering the means to increase the efficacy of BRAFi and to prevent or overcome BRAFi-resistance. We explored the role of p21-activated kinases (PAKs), in particular PAK1, in BRAFi response. BRAFi lowered the levels of active PAK1 in treated cells. An activated form of PAK1 conferred BRAFi-resistance on otherwise sensitive cells, while genetic or pharmacologic suppression of PAK1 had a sensitizing effect. While activation of AKT1 and RAC1 proto-oncogenes increased BRAFi-tolerance, the protective effect was negated in the presence of PAK inhibitors. Furthermore, combining otherwise ineffective doses of PAK- and BRAF-inhibitors synergistically affected intrinsically BRAFi-resistant cells. Considering the high incidence of PAK1 activation in cancers, our findings suggests PAK inhibition as a strategy to augment BRAFi therapy and overcome some of the well-known resistance mechanisms.

Regulation of neuronal survival by DNA methyltransferases

The limited regenerative capacity of neuronal cells requires tight orchestration of cell death and survival regulation in the context of longevity, age-associated diseases as well as during the development of the nervous system. Subordinate to genetic networks epigenetic mechanisms like DNA methylation and histone modifications are involved in the regulation of neuronal development, function and aging. DNA methylation by DNA methyltransferases (DNMTs), mostly correlated with gene silencing, is a dynamic and reversible process. In addition to their canonical actions performing cytosine methylation, DNMTs influence gene expression by interactions with histone modifying enzymes or complexes increasing the complexity of epigenetic transcriptional networks. DNMTs are expressed in neuronal progenitors, post-mitotic as well as adult neurons. In this review, we discuss the role and mode of actions of DNMTs including downstream networks in the regulation of neuronal survival in the developing and aging nervous system and its relevance for associated disorders.

Pegylated IFN-α suppresses hepatitis C virus by promoting the DAPK-mTOR pathway

Death-associated protein kinase (DAPK) has been found to be induced by IFN, but its antiviral activity remains elusive. Therefore, we investigated whether DAPK plays a role in the pegylated IFN-α (peg-IFN-α)-induced antiviral activity against hepatitis C virus (HCV) replication. Primary human hepatocytes, Huh-7, and infectious HCV cell culture were used to study the relationship between peg-IFN-α and the DAPK-mammalian target of rapamycin (mTOR) pathways. The activation of DAPK and signaling pathways were determined using immunoblotting. By silencing DAPK and mTOR, we further assessed the role of DAPK and mTOR in the peg-IFN-α-induced suppression of HCV replication. Peg-IFN-α up-regulated the expression of DAPK and mTOR, which was associated with the suppression of HCV replication. Overexpression of DAPK enhanced mTOR expression and then inhibited HCV replication. In addition, knockdown of DAPK reduced the expression of mTOR in peg-IFN-α-treated cells, whereas silencing of mTOR had no effect on DAPK expression, suggesting mTOR may be a downstream effector of DAPK. More importantly, knockdown of DAPK or mTOR significantly mitigated the inhibitory effects of peg-IFN-α on HCV replication. In conclusion, our data suggest that the DAPK-mTOR pathway is critical for anti-HCV effects of peg-IFN-α.

Suppression of FoxO6 by lipopolysaccharide in aged rat liver

The beneficial role of FoxO during aging has been proposed for its promotion of resistance to oxidative stress and inhibition of pro-inflammatory mediators. On the other hand, NF-κB is a pro-inflammatory transcription factor which is a key mediator of inflammatory cytokine generation. However, the correlation between FoxO6 and NF-κB during aging has not fully been explored.

The main purpose of the present study was to elucidate mechanisms underlying the protective role of FoxO6 in the maintenance of cellular homeostasis under potent pro-inflammatory conditions induced by LPS. Initial experimentation revealed that reduced FoxO6 activity during aging was caused by its phosphorylation, which suppressed its transcriptional activity in aged livers. Transfection with FoxO6-wt virus and FoxO6-siRNA in HepG2 cells revealed that FoxO6 phosphorylation by LPS leads to NF-κB activation via Akt and Pak1 pathways. Furthermore, Pak1 activity was increased in a phosphatidylinositol 3-kinase independent manner, and LPS-induced FoxO6 phosphorylation and FoxO6 inactivation were Pak1-dependent in nuclear fractions of cells. Further revealed Pak1 phosphorylation by LPS permitted interaction between FoxO6 and Akt.

Current study suggests FoxO6 phosphorylation facilitates the nuclear translocation of NF-κB via Akt and Pak1 pathways induced by LPS in aged rats.

Down-regulation of p21-activated serine/threonine kinase 1 is involved in loss of mesencephalic dopamine neurons

BACKGROUND

Although the roles of p21-activated serine/threonine kinase 1 (PAK1) have been reported in some neurodegenerative diseases, details regarding neurodegeneration are still limited. Hence, we tried to determine the role of PAK1 and molecular mechanisms of neuronal death involved in neurodegeneration.

RESULTS

Expression of a dominant-negative form of PAK1 (PAK1(H83,86L, K229R), PAK1-DN) decreased the cell viability and increased cell death induced by oxidative stress. Indeed, oxidative stress decreased the phosphorylation of PAK1 in neuroblastoma cells, cultured dopamine (DA) neurons, or rat midbrains. PAK1-DN reduced the level of Bcl-2 protein, through an ubiquitin/proteasome-dependent mechanism. The level of Bcl-2 may be regulated by PAK1-ERK signaling and/or PAK1, directly. Conversely, expression of an active form of PAK1 (PAK1(T423E), PAK1-CA) could recover both loss of DA neurons in the substantia nigra (SN) and behavioral defects in a 6-OHDA-induced hemiparkinsonian rat model.

CONCLUSIONS

Our data suggest that the oxidative stress-induced down-regulation of PAK1 activity could be involved in the loss of mesencephalic DA neurons through modulation of neuronal death, suggesting a novel role of PAK1 as a molecular determinant and mechanisms in the pathogenesis of Parkinson's disease.

A Crosstalk Between K ras (Kirsten Rat Sarcoma Viral Oncogene Homologue) and Adherence Molecular Complex Leads to Disassociation of Cells-A Possible Contribution Towards Metastasis in Colorectal Cancer

Constitutive activation of mutant K ras (Kirsten rat sarcoma viral oncogene homologue) and disassembly of E-cadherin-catenin complex (E-cadherin, α-catenin, β-catenin, and γ-catenin) play an important role in apoptosis, differentiation, and cell proliferation. In this study, the expression pattern of K ras and E-cadherin-catenin complex has been evaluated in normal and mutant colorectal cancer cell lines with an object to determine its impact on disassociation of cells from one another. We addressed the expression analysis of K ras with reference to its association with adherence molecules in two colorectal cancer cell lines, that is, Caco-2 (wild type K ras served as a control) and DLD1 (heterozygous mutation at codon 13) at message level by qRT-PCR and translational level by western blotting. Compared to the control Caco-2 cell lines, the K ras in DLD1 cell lines showed slightly higher values while α-catenin showed a slight lower (1.3-folds), β-catenin and E-cadherin showed significantly lower expression (4.2-fold decrease). It can be inferred that a possible cross talk exists between K ras and adherent junction mediated signalling. Mutation at codon 13 (G to D) leads to the overexpression of K ras and reduced expression of adherent junction complex resulting in metastasis. J. Cell. Biochem. 117: 2340-2345, 2016. © 2016 Wiley Periodicals, Inc.

Herbal Extracts Induce Dermal Papilla Cell Proliferation of Human Hair Follicles

BACKGROUND

The number of people suffering from balding or hair thinning is increasing, despite the advances in various medical therapies. Therefore, it is highly important to develop new therapies to inhibit balding and increase hair proliferation.

OBJECTIVE

We investigated the effects of herbal extracts commonly used for improving balding in traditional medicine to identify potential agents for hair proliferation.

METHODS

The expression levels of 5α-reductase isoforms (type I and II) were analyzed using quantitative real-time reverse transcription polymerase chain reaction in the human follicular dermal papilla cells (DPCs). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylteterazolium bromide and bromodeoxyuridine tests were used to evaluate the cell proliferation effect of herbal extracts in DPCs. The expression levels of extracellular signal-regulated kinase (ERK), Akt, cyclin D1, cyclin-dependent kinase 4 (Cdk4), B-cell lymphoma (Bcl-2) and Bcl-2-associated X protein (Bax) were measured using western blot analysis.

RESULTS

The 5α-reductase isoform mRNAs and proteins were detected in the cultured DPCs, and the expression level of 5α-R2 in DPCs in the presence of the herbal extracts was gradually decreased. Herbal extracts were found to significantly increase the proliferation of human DPCs at concentrations ranging from 1.5% to 4.5%. These results show that the herbal extracts tested affected the protein expressions of ERK, Akt, cyclin D1, Cdk4, Bcl-2, and Bax in DPCs.

CONCLUSION

These results suggest that herbal extracts exert positive effects on hair proliferation via ERK, Akt, cyclin D1, and Cdk4 signaling in DPCs; they also suggest that herbal extracts could be a great alternative therapy for increasing hair proliferation.

Clinical use of conditioned media of adipose tissue-derived stem cells in female pattern hair loss: a retrospective case series study

BACKGROUND

Female pattern hair loss (FPHL) is a common disorder but presents severe psychosocial problems in many female patients. Adipose tissue-derived stem cells (ADSCs) and conditioned media of ADSCs (ADSC-CM) are reported to promote hair growth in vitro. However, there are no clinical reports on the treatment of alopecia using ADSC-CM.

OBJECTIVES

This study evaluates our clinical experience in the use of ADSC-CM for the treatment of FPHL.

METHODS

A retrospective, observational study of outcomes in 27 patients with FPHL treated with ADSC-CM was performed. To evaluate the efficacy of the treatment, patients' medical records and phototrichographic images were analyzed.

RESULTS

The application of ADSC-CM showed efficacy in treating FPHL after 12 weeks of therapy. Hair density increased from 105.4 to 122.7 hairs/cm(2) (P < 0.001). Hair thickness increased from 57.5 μm to 64.0 μm (P < 0.001). None of the patients reported severe adverse reactions.

CONCLUSIONS

The application of ADSC-CM is a potential treatment option for FPHL.

Potential compensation among group I PAK members in hindlimb ischemia and wound healing

PAKs are serine/threonine kinases that regulate cytoskeletal dynamics and cell migration. PAK1 is activated by binding to the small EF hand protein, CIB1, or to the Rho GTPases Rac1 or Cdc42. The role of PAK1 in angiogenesis was established based only on in vitro studies and its role in angiogenesis in vivo has never been examined. Here we tested the hypothesis that PAK1 is an essential regulator of ischemic neovascularization (arteriogenesis and angiogenesis) and wound healing using a global PAK1 knockout mouse. Neovascularization was assessed using unilateral hindlimb ischemia. We found that plantar perfusion, limb use and appearance were not significantly different between 6-8 week old PAK1-/- and PAK1+/+ mice throughout the 21-day period following hindlimb ischemia; however a slightly delayed healing was observed in 16 week old PAK1-/- mice. In addition, the wound healing rate, as assessed with an ear punch assay, was unchanged in PAK1-/- mice. Surprisingly, however, we observed a notable increase in PAK2 expression and phosphorylation in ischemic gastrocnemius tissue from PAK1-/- but not PAK1+/+ mice. Furthermore, we observed higher levels of activated ERK2, but not AKT, in ischemic and non-ischemic muscle of PAK1-/- mice upon hindlimb ischemic injury. A group I PAK inhibitor, IPA3, significantly inhibited endothelial cell sprouting from aortic rings in both PAK1-/- and PAK1+/+ mice, implying that PAK2 is a potential contributor to this process. Taken together, our data indicate that while PAK1 has the potential to contribute to neovascularization and wound healing, PAK2 may functionally compensate when PAK1 is deficient.

Modulation of the mevalonate pathway by akt regulates macrophage survival and development of pulmonary fibrosis

Protein kinase B (Akt) is a key effector of multiple cellular processes, including cell survival. Akt, a serine/threonine kinase, is known to increase cell survival by regulation of the intrinsic pathway for apoptosis. In this study, we found that Akt modulated the mevalonate pathway, which is also linked to cell survival, by increasing Rho GTPase activation. Akt modulated the pathway by phosphorylating mevalonate diphosphate decarboxylase (MDD) at Ser(96). This phosphorylation in macrophages increased activation of Rac1, which enhanced macrophage survival because mutation of MDD (MDDS96A) induced apoptosis. Akt-mediated activation in macrophages was specific for Rac1 because Akt did not increase activity of other Rho GTP-binding proteins. The relationship between Akt and Rac1 was biologically relevant because Akt(+/-) mice had significantly less active Rac1 in alveolar macrophages, and macrophages from Akt(+/-) mice had an increase in active caspase-9 and -3. More importantly, Akt(+/-) mice were significantly protected from the development of pulmonary fibrosis, suggesting that macrophage survival is associated with the fibrotic phenotype. These observations for the first time suggest that Akt plays a critical role in the development and progression of pulmonary fibrosis by enhancing macrophage survival via modulation of the mevalonate pathway.

PAK signaling in cancer

Transformation of a normal cell to a cancer cell is caused by mutations in genes that regulate proliferation, apoptosis, and invasion. Small GTPases such as Ras, Rho, Rac and Cdc42 orchestrate many of the signals that are required for malignant transformation. The p21-activated kinases (PAKs) are effectors of Rac and Cdc42. PAKs are a family of serine/threonine protein kinases comprised of six isoforms (PAK1–6), and they play important roles in cytoskeletal dynamics, cell survival and proliferation. They act as key signal transducers in several cancer signaling pathways, including Ras, Raf, NFκB, Akt, Bad and p53. Although PAKs are not mutated in cancers, they are overexpressed, hyperactivated or amplified in several human tumors and their role in cell transformation make them attractive therapeutic targets. This review discusses the evidence that PAK is important for cell transformation and some key signaling pathways it regulates. This review primarily discusses Group I PAKs (PAK1, PAK2 and PAK3) as Group II PAKs (PAK4, PAK5 and PAK6) are discussed elsewhere in this issue (by Minden).

3D structure analysis of PAKs: A clue to the rational design for affinity reagents and blockers

The p21-activated kinase (PAK) family plays a versatile role in cell signaling by forming a hub of interactions. PAKs bind the GTPases like RAC and CDC42. Their proline-rich motifs bind SH3 adaptor proteins such as PIX and NCK. PAKs display nuclear localization signal sites and a potential Integrin binding site. No fully complete structure of the PAKs has been published; partial 3D structures of the PAK family kinases include portions of the auto-inhibited PAK1, GTPase bound to small peptides from PAKs, and the kinase domains from PAK1 and PAK4–6 (with small ligands in a few cases). This review focuses on exploring the intermolecular interaction regions in these 3D structures and we offer insights on the missing regions in crystal structure of the auto-inhibited PAK1. Understanding and modulation of PAK intermolecular interactions can pave the way for PAK blockers and biosensors.

PAK4-6 in cancer and neuronal development

PAKs 4, 5 and 6 are members of the group B family of p21-activated kinases. Among this group, PAK4 has been most extensively studied. While it has essential roles in embryonic development, in adults high levels of PAK4 are frequently associated with cancer. PAK4 is overexpressed in a variety of cancers, and the Pak4 gene is amplified in some cancers. PAK4 overexpression is sufficient to cause oncogenic transformation in cells and in mouse models. The tight connection between PAK4 and cancer make it a promising diagnostic tool as well as a potential drug target. The group B PAKs also have important developmental functions. PAK4 is important for many early developmental processes, while PAK5 and PAK6 play roles in learning and memory in mice. This chapter provides an overview of the roles of the group B PAKs in cancer as well as development, and includes a discussion of PAK mediated signaling pathways and cellular functions.

Ardisia crenata extract stimulates melanogenesis in B16F10 melanoma cells through inhibiting ERK1/2 and Akt activation

Melanin protects the skin against ultraviolet radiation by scattering incoming light and absorbing diverse free radicals. Agents that increase melanin synthesis in melanocytes may reduce the risk of photodamage and skin cancer. The present study investigated the effect of a methanol extract of Ardisia crenata (AC) on melanogenesis in B16F10 cells. Treatment of cultured B16F10 cells with AC extract (10, 20 and 40 µg/ml) stimulated an increase in melanin levels in a concentration-dependent manner, without cytotoxicity. Tyrosinase is key in the regulation of melanin production, thus the effect of AC extract on tyrosinase activity and protein expression was analyzed. AC extract was observed to significantly increase tyrosinase activity and protein expression in B16F10 cells. Furthermore, AC extract was found to markedly increase the protein expression of microphthalmia-associated transcription factor, which is an important transcription factor involved in tyrosinase gene expression. In addition, AC extract (40 µg/ml) was observed to suppress the activation of extracellular signal-regulated kinase (ERK) and Akt, which negatively regulate melanin synthesis in B16F10 cells. In conclusion, to the best of our knowledge, the present study is the first to show that a methanol extract of AC stimulates melanogenesis by increasing tyrosinase expression via the inhibition of ERK and Akt. Thus, methanol extract of AC may be a potential treatment for hypopigmentation diseases and may be a candidate for skin-tanning cosmetic products.

The role of p21-activated kinases in hepatocellular carcinoma metastasis

The p21-activated kinases (PAKs) are downstream effectors of the Rho family small GTPases as well as a wide variety of mitogenic factors and have been implicated in cancer formation, development and metastasis. PAKs phosphorylate a wide spectrum of substrates to mediate extracellular signals and regulate cytoskeletal remodeling, cell motility and survival. In this review, we aim to summarize the findings regarding the oncogenic role and the underlying mechanisms of PAKs signaling in various cancers, and in particular highlight the prime importance of PAKs in hepatocellular carcinoma (HCC) progression and metastasis. Recent studies exploring the potential therapeutic application of PAK inhibitors will also be discussed.

Demonstration and biological significance of a gastrin-P21-activated kinase 1 feedback loop in colorectal cancer cells

Gastrins, including amidated gastrin17 and glycine-extended gastrin17, are important growth factors in colorectal cancer (CRC). The p21-activated kinase 1 (PAK1) plays key roles in cellular processes including proliferation, survival, and motility, and in cell transformation and tumor progression. PAK1 expression increases with the progression of CRC, and knockdown of PAK1 blocks CRC cell growth and metastasis both in vitro and in vivo. The aim of this study was to determine the interaction between PAK1 and gastrins in CRC cells. PAK1 expression and activation were assayed by Western blots, and concentrations of gastrin mRNA and peptides by real-time PCR and radioimmunoassay, respectively. Proliferation of CRC cells was measured by (3)H-thymidine incorporation, and vascular endothelial growth factor : VEGF) secretion was measured by ELISA. Gastrins activated PAK1 via PI3K-dependent pathways. Activated PAK1 in turn mediated gastrin-stimulated activation of β-catenin and VEGF secretion in CRC cells, as knockdown of PAK1 blocked stimulation of these cellular processes by gastrins. Downregulation of gastrin reduced the expression and activity of PAK1, but in contrast there was a compensatory increase in gastrins either when PAK1 was downregulated, or after treatment with a PAK inhibitor. Our results indicate that PAK1 is required for the stimulation of CRC cells by gastrins, and suggest the existence of an inhibitory feedback loop by which PAK1 downregulates gastrin production in CRC cells.

An oncogenic kinase: putting PAK5 forward

INTRODUCTION

Overexpression of p21-activated kinase 5 (PAK5) is discovered in many tumors, probably due to its regulation in cytoskeleton, antiapoptosis and proliferation. A better understanding of the modulation mechanisms of PAK5 is needed for the development of tumor treatment where current therapeutics is inadequate.

AREAS COVERED

This review discusses the current understanding of PAK5 functions as an oncogenic kinase in tumor cellular regulation. Mechanisms of action and molecular pathways involved in cytoskeleton regulation, antiapoptosis and proliferation of tumors are discussed.

EXPERT OPINION

PAKs are serine/threonine kinases and downstream effectors for Cdc42 and Rac, the subfamilies of Rho small GTPases. PAK5 shares sequence identities in p21-GTPase-binding domain and kinase domain and is completely different in other regions compared with other PAKs. Overexpression of PAK5 has been found in several tumors, probably due to its contribution to proliferation, cytoskeleton and anti-apoptosis. Additional regulation mechanisms which are independent of Rho GTPases also indicate that PAK5 functions as a special signal molecule in cellular signaling pathways of tumor progression.

PAK4 confers cisplatin resistance in gastric cancer cells via PI3K/Akt- and MEK/ERK-dependent pathways

CDDP [cisplatin or cis-diamminedichloroplatinum(II)] and CDDP-based combination chemotherapy have been confirmed effective against gastric cancer. However, CDDP efficiency is limited because of development of drug resistance. In this study, we found that PAK4 (p21-activated kinase 4) expression and activity were elevated in gastric cancer cells with acquired CDDP resistance (AGS/CDDP and MKN-45/CDDP) compared with their parental cells. Inhibition of PAK4 or knockdown of PAK4 expression by specific siRNA (small interfering RNA)-sensitized CDDP-resistant cells to CDDP and overcome CDDP resistance. Combination treatment of LY294002 [the inhibitor of PI3K (phosphoinositide 3-kinase)/Akt (protein kinase B or PKB) pathway] or PD98509 {the inhibitor of MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase] pathway} with PF-3758309 (the PAK4 inhibitor) resulted in increased CDDP efficacy compared with LY294002 or PD98509 alone. However, after the concomitant treatment of LY294002 and PD98509, PF-3758309 administration exerted no additional enhancement of CDDP cytotoxicity in CDDP-resistant cells. Inhibition of PAK4 by PF-3758309 could significantly suppress MEK/ERK and PI3K/Akt signalling in CDDP-resistant cells. Furthermore, inhibition of PI3K/Akt pathway while not MEK/ERK pathway could inhibit PAK4 activity in these cells. The in vivo results were similar with those of in vitro. In conclusion, these results indicate that PAK4 confers CDDP resistance via the activation of MEK/ERK and PI3K/Akt pathways. PAK4 and PI3K/Akt pathways can reciprocally activate each other. Therefore, PAK4 may be a potential target for overcoming CDDP resistance in gastric cancer.

Pak and Rac GTPases promote oncogenic KIT-induced neoplasms

An acquired somatic mutation at codon 816 in the KIT receptor tyrosine kinase is associated with poor prognosis in patients with systemic mastocytosis and acute myeloid leukemia (AML). Treatment of leukemic cells bearing this mutation with an allosteric inhibitor of p21-activated kinase (Pak) or its genetic inactivation results in growth repression due to enhanced apoptosis. Inhibition of the upstream effector Rac abrogates the oncogene-induced growth and activity of Pak. Although both Rac1 and Rac2 are constitutively activated via the guanine nucleotide exchange factor (GEF) Vav1, loss of Rac1 or Rac2 alone moderately corrected the growth of KIT-bearing leukemic cells, whereas the combined loss resulted in 75% growth repression. In vivo, the inhibition of Vav or Rac or Pak delayed the onset of myeloproliferative neoplasms (MPNs) and corrected the associated pathology in mice. To assess the role of Rac GEFs in oncogene-induced transformation, we used an inhibitor of Rac, EHop-016, which specifically targets Vav1 and found that EHop-016 was a potent inhibitor of human and murine leukemic cell growth. These studies identify Pak and Rac GTPases, including Vav1, as potential therapeutic targets in MPN and AML involving an oncogenic form of KIT.

Activation of Rac1-PI3K/Akt is required for epidermal growth factor-induced PAK1 activation and cell migration in MDA-MB-231 breast cancer cells

Epidermal growth factor (EGF) may increase cell motility, an event implicated in cancer cell invasion and metastasis. However, the underlying mechanisms for EGF-induced cell motility remain elusive. In this study, we found that EGF treatment could activate Ras-related C3 botulinum toxin substrate 1 (Rac1), PI3K/Akt and p21-actived kinase (PAK1) along with cell migration. Ectopic expression of PAK1 K299R, a dominant negative PAK1 mutant, could largely abolish EGF-induced cell migration. Blocking PI3K/Akt signalling with LY294002 or Akt siRNA remarkably inhibited both EGF-induced PAK1 activation and cell migration. Furthermore, expression of dominant-negative Rac1 (T17N) could largely block EGF-induced PI3K/Akt-PAK1 activation and cell migration. Interestingly, EGF could induce a significant production of ROS, and N-acetyl-L-cysteine, a scavenger of ROS which abolished the EGF-induced ROS generation, cell migration, as well as activation of PI3K/Akt and PAK, but not Rac1. Our study demonstrated that EGF-induced cell migration involves a cascade of signalling events, including activation of Rac1, generation of ROS and subsequent activation of PI3K/Akt and PAK1.

Role of p21-activated kinases in cardiovascular development and function

p21-activated kinases (Paks) are a group of six serine/threonine kinases (Pak1-6) that are involved in a variety of biological processes. Recently, Paks, more specifically Pak1, -2, and -4, have been shown to play important roles in cardiovascular development and function in a range of model organisms including zebrafish and mice. These functions include proper morphogenesis and conductance of the heart, cardiac contractility, and development and integrity of the vasculature. The mechanisms underlying these effects are not fully known, but they likely differ among the various Pak isoforms and include both kinase-dependent and -independent functions. In this review, we discuss aspects of Pak function relevant to cardiovascular biology as well as potential therapeutic implications of small-molecule Pak inhibitors in cardiovascular disease.

Association of the epithelial-to-mesenchymal transition phenotype with responsiveness to the p21-activated kinase inhibitor, PF-3758309, in colon cancer models

The p21-activated kinase (PAK) family of serine/threonine kinases, which are overexpressed in several cancer types, are critical mediators of cell survival, motility, mitosis, transcription, and translation. In the study presented here, we utilized a panel of colorectal cancer (CRC) cell lines to identify potential biomarkers of sensitivity or resistance that may be used to individualize therapy to the PAK inhibitor PF-03758309. We observed a wide range of proliferative responses in the CRC cell lines exposed to PF-03758309, this response was recapitulated in other phenotypic assays such as anchorage-independent growth, three-dimensional (3D) tumor spheroid formation, and migration. Interestingly, we observed that cells most sensitive to PF-03758309 exhibited up-regulation of genes associated with a mesenchymal phenotype (CALD1, VIM, ZEB1) and cells more resistant had an up-regulation of genes associated with an epithelial phenotype (CLDN2, CDH1, CLDN3, CDH17) allowing us to derive an epithelial-to-mesenchymal transition (EMT) gene signature for this agent. We assessed the functional role of EMT-associated genes in mediating responsiveness to PF-3758309, by targeting known genes and transcriptional regulators of EMT. We observed that suppression of genes associated with the mesenchymal phenotype conferred resistance to PF-3758309, in vitro and in vivo. These results indicate that PAK inhibition is associated with a unique response phenotype in CRC and that further studies should be conducted to facilitate both patient selection and rational combination strategies with these agents.

The response to PAK1 inhibitor IPA3 distinguishes between cancer cells with mutations in BRAF and Ras oncogenes

While new drugs aimed at BRAF-mutated cancers are entering clinical practice, cells and tumors with activating Ras mutations are relatively resistant to those and quite a few other anti-cancer agents. This inspires the effort to reverse this resistance or to uncover new vulnerabilities in such resistant cancers. IPA3 has been originally identified as a small molecule inhibitor of p21-activated protein kinase 1 (PAK1), a candidate therapeutic target in human malignancies. We have tested a battery of melanoma and colon carcinoma cell lines that carry mutations in BRAF, NRAS and KRAS genes and have observed that those with NRAS and KRAS mutations are more sensitive to killing by IPA3. Genetic manipulations suggest that the differential response depends not just on these oncogenes, but also on additional events that were co-selected during tumor evolution. Furthermore, sublethal doses of IPA3 or ectopic expression of dominant-negative PAK1 sensitized Ras-mutated cells to GDC-0897 and AZD6244, which otherwise have reduced efficiency against cells with activated Ras. Dominant-negative PAK1 also reduced the growth of NRAS-mutated cells in confluent cultures, but, unlike IPA3, caused no significant toxicity. Although it remains to be proven that all the effects of IPA3 are exclusively due to inhibition of PAK1, our findings point to the existence of selective vulnerabilities, which are associated with Ras mutations and could be useful for better understanding and treatment of a large subset of tumors.

p-21-Activated kinase 1 mediates gastrin-stimulated proliferation in the colorectal mucosa via multiple signaling pathways

Gastrins, including amidated (Gamide) and glycine-extended (Ggly) forms, function as growth factors for the gastrointestinal mucosa. The p-21-activated kinase 1 (PAK1) plays important roles in growth factor signaling networks that control cell motility, proliferation, differentiation, and transformation. PAK1, activated by both Gamide and Ggly, mediates gastrin-stimulated proliferation and migration, and activation of β-catenin, in gastric epithelial cells. The aim of this study was to investigate the role of PAK1 in the regulation by gastrin of proliferation in the normal colorectal mucosa in vivo. Mucosal proliferation was measured in PAK1 knockout (PAK1 KO) mice by immunohistochemistry. The expression of phosphorylated and unphosphorylated forms of the signaling molecules PAK1, extracellular signal-regulated kinase (ERK), and protein kinase B (AKT), and the expression of β-catenin and its downstream targets c-Myc and cyclin D1, were measured in gastrin knockout (Gas KO) and PAK1 KO mice by Western blotting. The expression and activation of PAK1 are decreased in Gas KO mice, and these decreases are associated with reduced activation of ERK, AKT, and β-catenin. Proliferation in the colorectal mucosa of PAK1 KO mice is reduced, and the reduction is associated with reduced activation of ERK, AKT, and β-catenin. In compensation, antral gastrin mRNA and serum gastrin concentrations are increased in PAK1 KO mice. These results indicate that PAK1 mediates the stimulation of colorectal proliferation by gastrins via multiple signaling pathways involving activation of ERK, AKT, and β-catenin.

Atorvastatin requires geranylgeranyl transferase-I and Rac1 activation to exert neuronal protection and induce plasticity

Statins are widely used cholesterol-lowering drugs that may reduce the incidence of stroke and the progression of Alzheimer's disease (AD). However, how statins exert these beneficial effects remains poorly understood. Thus, this study evaluated the roles of Rac1 geranylgeranylation and the relationship between Rac1 and αN-catenin in the protective activity of atorvastatin (ATV) in a cortical neuronal culture model of glutamate (GLU) excitotoxicity. We found that ATV-induced neuroprotection and plasticity were blocked by isoprenoids, such as farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), inhibition of farnesylation (FTI-277) and geranylgeranylation (GGTI-286), down-regulation of GGTase-Iβ and Rac activity and promotion of active RhoA. Additionally, ATV rescued the distribution of dendritic αN-catenin and increased the number and length of dendritic branches; these effects were reversed by GGTI-286, GGTase-Iβ shRNA, Rac1 shRNA and a dominant-negative version of Rac1 (T17N). In summary, our findings suggest that ATV requires GGTase-Iβ, prenylation and active Rac1 to induce protection and plasticity. In this regard, αN-catenin is a marker for stable interactions between adhesion proteins and the actin cytoskeleton and is necessary for the neuroprotective action of ATV.

[6]-Shogaol inhibits melanogenesis in B16 mouse melanoma cells through activation of the ERK pathway

AIM

To investigate the effect of [6]-shogaol, an active ingredient in ginger, on melanogenesis and the underlying mechanisms.

METHODS

B16F10 mouse melanoma cells were tested. Cell viability was determined with the MTT assay. Melanin content and tyrosinase activity were analyzed with a spectrophotometer. The protein expression of tyrosinase and microphthalmia associated transcription factor (MITF), as well as phosphorylated or total ERK1/2 and Akt were measured using Western blot.

RESULTS

Treatment of the cells with [6]-shogaol (1, 5, 10 μmol/L) reduced the melanin content in a concentration-dependent manner. [6]-Shogaol (5 and 10 μmol/L) significantly decreased the intracellular tyrosinase activity, and markedly suppressed the expression levels of tyrosinase and MITF proteins in the cells. Furthermore, [6]-shogaol (10 μmol/L) activated ERK, which was known to negatively regulate melanin synthesis in these cells. Pretreatment with the specific ERK pathway inhibitor PD98059 (20 μmol/L) greatly attenuated the inhibition of melanin synthesis by [6]-shogaol (10 μmol/L).

CONCLUSION

The results demonstrate that [6]-shogaol inhibits melanogenesis in B16F10 mouse melanoma cells via activating the ERK pathway.

Proapoptotic effects of the chemokine, CXCL 10 are mediated by the noncognate receptor TLR4 in hepatocytes

Aberrant expression of the chemokine CXC chemokine ligand (CXCL)10 has been linked to the severity of hepatitis C virus (HCV)-induced liver injury, but the underlying molecular mechanisms remain unclear. In this study, we describe a yet-unknown proapoptotic effect of CXCL10 in hepatocytes, which is not mediated through its cognate chemokine receptor, but the lipopolysaccharide receptor Toll-like receptor 4 (TLR4). To this end, we investigated the link of CXCL10 expression with apoptosis in HCV-infected patients and in murine liver injury models. Mice were treated with CXCL10 or neutralizing antibody to systematically analyze effects on hepatocellular apoptosis in vivo. Direct proapoptotic functions of CXCL10 on different liver cell types were evaluated in detail in vitro. The results showed that CXCL10 expression was positively correlated with liver cell apoptosis in humans and mice. Neutralization of CXCL10 ameliorated concanavalin A-induced tissue injury in vivo, which was strongly associated with reduced liver cell apoptosis. In vitro, CXCL10 mediated the apoptosis of hepatocytes involving TLR4, but not CXC chemokine receptor 3 signaling. Specifically, CXCL10 induced long-term protein kinase B and Jun N-terminal kinase activation, leading to hepatocyte apoptosis by caspase-8, caspase-3, and p21-activated kinase 2 cleavage. Accordingly, systemic application of CXCL10 led to TLR4-induced liver cell apoptosis in vivo.

CONCLUSION

The results identify CXCL10 and its noncognate receptor, TLR4, as a proapoptotic signaling cascade during liver injury. Antagonism of the CXCL10/TLR4 pathway might be a therapeutic option in liver diseases associated with increased apoptosis.

P21-activated protein kinase 1 (Pak1) mediates the cross talk between insulin and β-catenin on proglucagon gene expression and its ablation affects glucose homeostasis in male C57BL/6 mice

In gut endocrine L cells, the Wnt signaling pathway effector β-catenin (β-cat)/transcription factor 7-like 2 mediates the stimulatory effect of insulin on proglucagon (gcg) expression and glucagon-like peptide-1 (GLP-1) production. In several other cell lineages, insulin is able to stimulate p21-activated protein kinase 1 (Pak1). Here we determined the role of Pak1 in gcg expression and the effect of Pak1 deletion on glucose homeostasis. Insulin stimulated Pak1 activation through increasing its Thr423 phosphorylation in gut gcg-expressing cell lines, associated with increased gcg mRNA levels. This stimulation was attenuated by the Pak inhibitor 2,2'-dihydroxy-1,1'-dinaphthyldisulfide (IPA3) or dominant-negative Pak1. Both insulin and cAMP-promoting agents activated β-cat Ser675 phosphorylation, which was attenuated by IPA3 or protein kinase A inhibition, respectively. Gut gcg levels were reduced in male Pak1(-/-) mice, associated with impaired glucose tolerance after an ip or oral glucose challenge. These mice had lower circulating active GLP-1 levels after a glucose challenge as well as reduced distal ileum GLP-1 content after insulin treatment. Finally, the Pak1(-/-) mice exhibited reduced brainstem gcg level and abolished β-cat Ser675 phosphorylation in brain neurons after insulin treatment. We suggest that Pak1 mediates the cross talk between insulin and Wnt signaling pathways on gut and brain gcg expression, and its ablation impairs glucose homeostasis.