Tadashi Igishi

A Novel PDZ Domain Containing Guanine Nucleotide Exchange Factor Links Heterotrimeric G Proteins to Rho

Small GTP-binding proteins of the Rho family play a critical role in signal transduction. However, there is still very limited information on how they are activated by cell surface receptors. Here, we used a consensus sequence for Dbl domains of Rho guanine nucleotide exchange factors (GEFs) to search DNA data bases, and identified a novel human GEF for Rho-related GTPases harboring structural features indicative of its possible regulatory mechanism(s). This protein contained a tandem DH/PH domain closely related to those of Rho-specific GEFs, a PDZ domain, a proline-rich domain, and an area of homology to Lsc, p115-RhoGEF, and a Drosophila RhoGEF that was termed Lsc-homology (LH) domain. This novel molecule, designated PDZ-RhoGEF, activated biological and biochemical pathways specific for Rho, and activation of these pathways required an intact DH and PH domain. However, the PDZ domain was dispensable for these functions, and mutants lacking the LH domain were more active, suggesting a negative regulatory role for the LH domain. A search for additional molecules exhibiting an LH domain revealed a limited homology with the catalytic region of a newly identified GTPase-activating protein for heterotrimeric G proteins, RGS14. This prompted us to investigate whether PDZ-RhoGEF could interact with representative members of each G protein family. We found that PDZ-RhoGEF was able to form, in vivo, stable complexes with two members of the Gα12 family, Gα12 and Gα13, and that this interaction was mediated by the LH domain. Furthermore, we obtained evidence to suggest that PDZ-RhoGEF mediates the activation of Rho by Gα12 and Gα13. Together, these findings suggest the existence of a novel mechanism whereby the large family of cell surface receptors that transmit signals through heterotrimeric G proteins activate Rho-dependent pathways: by stimulating the activity of members of the Gα12 family which, in turn, activate an exchange factor acting on Rho.

Signaling from the Small GTP-binding Proteins Rac1 and Cdc42 to the c-Jun N-terminal Kinase/Stress-activated Protein Kinase Pathway A ROLE FOR MIXED LINEAGE KINASE 3/PROTEIN-TYROSINE KINASE 1, A NOVEL MEMBER OF THE MIXED LINEAGE KINASE FAMILY

Certain small GTP-binding proteins control the enzymatic activity of a family of closely related serine-threonine kinases known as mitogen-activated protein kinases (MAPKs). In turn, these MAPKs, such as p44mapk and p42mapk, referred to herein as MAPKs, and stress-activated protein kinases, also termed c-Jun N-terminal kinases (JNKs), phosphorylate and regulate the activity of key molecules that ultimately control the expression of genes essential for many cellular processes. Whereas Ras controls the activation of MAPK, we and others have recently observed that two members of the Rho family of small GTP-binding proteins, Rac1 and Cdc42, regulate the activity of JNKs. The identity of molecules communicating Rac1 and Cdc42 to JNK is still poorly understood. It has been suggested that Pak1 is the most upstream kinase connecting these GTPases to JNK; however, we have observed that coexpression of Pak1 with activated forms of Cdc42 or Rac1 diminishes rather than enhances JNK activation. This prompted us to explore the possibility that kinases other than Pak might participate in signaling from GTP-binding proteins to JNK. In this regard, a computer-assisted search for proteins containing areas of homology to that in Pak1 that is involved in binding to Rac1 and Cdc42 led to the identification of mixed lineage kinase 3 (MLK3), also known as protein-tyrosine kinase 1, as a potential candidate for this function. In this study, we found that MLK3 overexpression is sufficient to activate JNK potently without affecting the phosphorylating activity of MAPK or p38. Furthermore, we present evidence that MLK3 binds the GTP-binding proteins Cdc42 and Rac1 in vivo and that MLK3 mediates activation of MEKK-SEK-JNK kinase cascade by Rac1 and Cdc42. Taken together, these findings strongly suggest that members of the novel MLK family of highly related kinases link small GTP-binding proteins to the JNK signaling pathway.

Correlation between Asian dust storms and worsening asthma in Western Japan.

BACKGROUND Severe wind storms during spring in East Asia, called Asian dust storms (ADS), have been assessed in the past for their effect on health in Asian countries. Our objective was to study the ADS association with asthma symptoms in adult patients in Japan. METHODS We designed a telephone survey to assess ADS influence on upper and lower respiratory, ocular and cutaneous symptoms in 98 patients with adult asthma from April to May 2007. Peak expiratory flow (PEF) was also measured from February to May. RESULTS Worsening lower respiratory symptoms were noted by 22 of 98 patients during ADS in April, when Japanese cedar pollen levels also increased. During ADS in May, however, Japanese cedar and cypress pollen levels were not elevated, 11 patients had worsening of lower respiratory symptoms. None required emergency treatment for the exacerbation. Lower respiratory symptoms worsening most were cough and sputum; this was more common in patients with allergic rhinitis or atopy than in those without (P < 0.05). Min%Max differed significantly at 88.7 ± 6.6% during dust dispersion period, defined as the ADS day plus the next 6 days, versus 92.0 ± 5.3% during the 7-day period before a dust storm. CONCLUSIONS We found that ADS aggravated lower respiratory symptoms in adult patients with asthma, but this influence was mild.BACKGROUND Severe wind storms during spring in East Asia, called Asian dust storms (ADS), have been assessed in the past for their effect on health in Asian countries. Our objective was to study the ADS association with asthma symptoms in adult patients in Japan. METHODS We designed a telephone survey to assess ADS influence on upper and lower respiratory, ocular and cutaneous symptoms in 98 patients with adult asthma from April to May 2007. Peak expiratory flow (PEF) was also measured from February to May. RESULTS Worsening lower respiratory symptoms were noted by 22 of 98 patients during ADS in April, when Japanese cedar pollen levels also increased. During ADS in May, however, Japanese cedar and cypress pollen levels were not elevated, 11 patients had worsening of lower respiratory symptoms. None required emergency treatment for the exacerbation. Lower respiratory symptoms worsening most were cough and sputum; this was more common in patients with allergic rhinitis or atopy than in those without (P <0.05). Min%Max differed significantly at 88.7 ± 6.6% during dust dispersion period, defined as the ADS day plus the next 6 days, versus 92.0 ± 5.3% during the 7-day period before a dust storm. CONCLUSIONS We found that ADS aggravated lower respiratory symptoms in adult patients with asthma, but this influence was mild.

Divergent Signaling Pathways Link Focal Adhesion Kinase to Mitogen-activated Protein Kinase Cascades EVIDENCE FOR A ROLE OF PAXILLIN IN c-Jun NH2-TERMINAL KINASE ACTIVATION

Stimulation of a number of cell surface receptors, including integrins and G protein-coupled receptors, results in the activation of a non-receptor tyrosine kinase known as focal adhesion kinase (FAK). In turn, this kinase is believed to play a critical role in signaling to intracellular kinase cascades controlling gene expression such as extracellular signal-regulated kinases (ERKs), by a yet poorly defined mechanism. Furthermore, whether this tyrosine kinase also mediates the activation of other mitogen-activated protein kinase family members, such as c-Jun NH2-terminal kinases (JNKs), is still unclear. We show here that the activation of FAK by anchoring to the cell membrane is itself sufficient to stimulate potently both ERK and JNK. These effects were found to be phosphatidylinositol 3-kinase-independent, as FAK effectively stimulated Akt, and wortmannin suppressed Akt but not ERK or JNK activation. As previously reported by others, activation of ERK correlated with the ability of FAK to induce tyrosine phosphorylation of Shc. Surprisingly, however, stimulation of JNK was not dependent on the kinase activity of FAK or on the ability to induce tyrosine phosphorylation of FAK substrates. Instead, we provide evidence that FAK may stimulate JNK through a novel pathway involving the recruitment of paxillin to the plasma membrane and the subsequent activation of a biochemical route dependent on small GTP-binding proteins of the Rho family.

Sulindac sulfide and caffeic acid phenethyl ester suppress the motility of lung adenocarcinoma cells promoted by transforming growth factor-β through Akt inhibition

Abstract Cell migration is essential for invasive and metastatic phenotypes of cancer cells. Potential chemopreventive agents of cancer—sulindac sulfide, caffeic acid phenethyl ester (CAPE), curcumin, and (+)-catechin—have been reported to interfere with several types of intracellular signaling. In this study, we examined the effects of these agents on transforming growth factor-β(TGF-β)-induced motility and Akt phosphorylation in A549 cells. Judged by gold particle phagokinesis assay, sulindac sulfide, CAPE, and curcumin suppressed the motility of A549 cells promoted by TGF-β. LY294002, a specific inhibitor of phosphatidylinositol 3-kinase(PI3K)/Akt signaling, also suppressed TGF-β-induced motility and Akt phosphorylation. Sulindac sulfide and CAPE, but not curcumin, suppressed TGF-β-induced Akt phosphorylation. We conclude that sulindac sulfide and CAPE suppress the motility promoted by TGF-β in lung adenocarcinoma cells through the suppression of Akt. Our observations raise the possibility that these agents, except for (+)-catechin, can be applied not only as chemopreventive agents but also as anti-metastatic therapy.

Elevated urinary 8‐hydroxydeoxyguanosine, a biomarker of oxidative stress, and lack of association with antioxidant vitamins in chronic obstructive pulmonary disease

Objective:  The purpose of this study was to investigate whether patients with COPD are under oxidative stress and to elucidate the relationship between the level of oxidative stress and antioxidant vitamins.

Pollen Augments the Influence of Desert Dust on Symptoms of Adult Asthma Patients

BACKGROUND East Asian desert dust storms that occur during mainly spring are called Asian dust storms (ADS). Our objective was to study the association of pollen and ADS with symptoms of adult asthma patients in Japan. METHODS We designed a telephone survey to investigate the upper and lower respiratory, ocular, and skin symptoms of asthma patients during ADS in February, March, and December on 2009. Peak expiratory flow (PEF) was also measured from February to May. RESULTS We surveyed 106 patients in February, 101 patients in March, and 103 patients in December. In February and March, Japanese cedar and/or cypress pollen was also in the atmosphere during ADS, but no pollen was identified during December survey. Worsening of upper or lower respiratory, ocular, or skin symptoms was noted by 20.8% of patients in February, 33.7% in March, and 16.5% in December. Worsening of symptoms was significantly more common in March than in February or December. Two patients needed emergency treatment for exacerbation during ADS in March, but no patient needed hospitalization in any period. There was no significant difference of the daily morning PEF/personal best PEF ratio between ADS days and control days. However, in patients with worsening of upper and/or lower respiratory tract symptoms, the daily morning PEF/personal best ratio was significantly associated with the atmospheric level of particulate matter, but not with levels of pollen or other air pollutants. CONCLUSIONS Pollen augmented symptoms in adult asthma patients, but ADS on its own also were able to aggravate symptoms and pulmonary function.

Phase II Study of Weekly Paclitaxel in Patients with Non-Small Cell Lung Cancer Who Have Failed Previous Treatments

Objective: New effective therapy is desirable for patients with non-small cell lung cancer (NSCLC) who have failed previous treatments. Fractionated administration of paclitaxel may be less toxic and more active against NSCLC. The aim of this study was to evaluate the activity and toxicity of weekly paclitaxel therapy for NSCLC in a second-line setting. Methods: Patients with pathological or cytological diagnosis of NSCLC, measurable lesions, and one or more prior therapies were enrolled. We administered weekly infusions of 80 mg/m2 paclitaxel 3 times in a 4-week cycle. In the absence of progressive disease or intolerable toxicity, each patient was treated for a minimum of 4 cycles. Results: Of 39 patients enrolled, 1 patient achieved complete response and 11 patients achieved partial response (response rate, 31%: 95% confidence interval, 17–48%). The median survival time was 43 weeks (range, 7–128 weeks). Grade 3 or 4 leukopenia occurred in only 7 patients (18%). Neurotoxicity was the most frequent adverse effect (grades 1 and 2.26 and 5%, respectively). Although all patients recovered rapidly with corticosteroid treatment, drug-induced pneumonitis was observed in 3 patients (8%). Conclusion: Low-dose weekly paclitaxel is a promising therapy with high effectiveness for advanced NSCLC in patients with NSCLC who have failed previous treatments.

Phase II Trial of Weekly Paclitaxel in Previously Untreated Advanced Non-Small-Cell Lung Cancer

Objective: New effective therapy is desirable for outpatients with advanced non-small-cell lung cancer (NSCLC). Fractionated administration of paclitaxel may be less toxic and more active against NSCLC. The aim of this study was to evaluate the activity and toxicity of weekly paclitaxel therapy for chemotherapy-naive NSCLC. Methods: Patients with pathological or cytological diagnosis of NSCLC, measurable lesions, and no prior therapy were enrolled. We administered weekly infusions of 80 mg/m2 paclitaxel 3 times in a 4-week cycle. In the absence of progressive disease or intolerable toxicity, we treated each patient for a minimum of four cycles. Results: Of 35 patients enrolled, 17 patients achieved partial response, although no complete responses were observed (response rate 49%; 95% confidence interval 32–66%). The median survival time was 55 weeks (range 6–93 weeks). Grade 3 or 4 leukopenia occurred in only 1 patient (3%). Neurotoxicity was the most frequent adverse effect (grades 1 and 2, 26 and 3%, respectively). Serious toxicity, observed in 2 patients (6%), was interstitial pneumonia, and 1 patient died from sequela. Conclusion: Low-dose weekly paclitaxel is a promising therapy for advanced NSCLC with high effectiveness and low toxicity.

Effects on asthma and induction of interleukin-8 caused by Asian dust particles collected in western Japan.

Abstract Objective: Asian dust storms (ADS) contain various airborne particles that may augment airway inflammation by increasing the level of interleukin-8. The objective of the study was to investigate the association of exposure to an ADS with worsening of symptoms of adult asthma and the effect of ADS particles on interleukin-8 transcriptional activity. Methods: The subjects were 112 patients with mild to moderate asthma who recorded scores for their daily upper and lower respiratory tract symptoms and measured morning peak expiratory flow (PEF) from March to May 2011. Interleukin-8 transcriptional activity was assessed in THP-G8 cells that were exposed to airborne particles collected during days of ADS exposure. Results: Of the 112 patients, 31 had comorbid allergic rhinitis (AR) and/or chronic sinusitis (CS), and had worsened scores for upper respiratory tract symptoms on ADS days compared to non-ADS days. Scores for lower respiratory tract symptoms during ADS days were higher than non-ADS days in all patients. Three patients also had unscheduled hospital visits for exacerbation of asthma on ADS days. However, there was no significant difference in daily morning PEF between ADS and non-ADS days. Airborne particles collected on ADS days induced interleukin-8 transcriptional activity in THP-G8 cells compared to the original soil of the ADS. Conclusion: Exposure to an ADS aggravates upper and lower tract respiratory symptoms in patients with adult asthma. ADS airborne particles may increase airway inflammation through enhancement of interleukin-8 transcriptional activity.