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Biomedical subjects

K Vuori

Publications and source records attributed to K Vuori.

At least 19 recordsLinked to original sources
PubMed2004

Neuroradiological findings (MRS, MRI, SPECT) in infantile neuronal ceroid-lipofuscinosis (infantile CLN1) at different stages of the disease.

Infantile neuronal ceroid-lipofuscinosis (infantile CLN1) is a progressive and uniformly fatal lysosomal storage disease of the nervous system. The purpose of this study was to compare the findings of various radiological examinations of the brain in the course of infantile CLN1 in order to evaluate the relative usefulness of the methods and their potential for monitoring therapeutic interventions. We examined eight infantile CLN1 patients, 51 studies, in various stages of the disease--preclinical to late stage--with proton magnetic resonance spectroscopy (1H-MRS), MRI, and perfusion SPECT, and in addition three benzodiazepine (BZ) receptor ligand SPECT studies. Both 1H-MRS and MRI showed abnormal findings before clinical manifestations of the disease. Cortical hypoperfusion and loss of cortical BZ receptors revealed by SPECT appeared simultaneously with clinical signs. After the age of 4 years MRI and SPECT alterations progressed minimally, whereas 1H-MRS showed progressive deterioration of neurometabolism. Of the four methods used in this study, MRI proved to be the most practicable for diagnosing infantile CLN1; the final diagnosis of infantile CLN1 is confirmed by the characteristic clinical picture and DNA or PPT enzyme analysis. The combination of 1H- MRS and MRI could be most useful for monitoring therapeutic interventions.

Aspartic Acid↗
PubMed2001

Integrin signaling inhibits paclitaxel-induced apoptosis in breast cancer cells.

Inherent or acquired drug resistance is one of the major problems in chemotherapy. The mechanisms by which cancer cells survive and escape the cytotoxic effects of chemotherapeutic agents are essentially unknown. In the present study, we demonstrate that in the MDA-MB-231 and MDA-MB-435 breast cancer cells, ligation of beta1 integrins by their extracellular matrix ligands inhibits significantly apoptosis induced by paclitaxel and vincristine, two microtubule-directed chemotherapeutic agents that are widely used in the therapy of breast cancer. We show that beta1 integrin signaling inhibits drug-induced apoptosis by inhibiting the release of cytochrome c from the mitochondria in response to drug treatment. Further, integrin-mediated protection from drug-induced apoptosis and inhibition of cytochrome c release are dependent on the activation of the PI 3-kinase/Akt pathway. Our results identify beta1 integrin signaling as an important survival pathway in drug-induced apoptosis in breast cancer cells and suggest that activation of this pathway may contribute to the generation of drug resistance.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Matrix attachment regulates Fas-induced apoptosis in endothelial cells: a role for c-flip and implications for anoikis.

Survival of endothelial cells is critical for cellular processes such as angiogenesis. Cell attachment to extracellular matrix inhibits apoptosis in endothelial cells both in vitro and in vivo, but the molecular mechanisms underlying matrix-induced survival signals or detachment-induced apoptotic signals are unknown. We demonstrate here that matrix attachment is an efficient regulator of Fas-mediated apoptosis in endothelial cells. Thus, matrix attachment protects cells from Fas-induced apoptosis, whereas matrix detachment results in susceptibility to Fas-mediated cell death. Matrix attachment modulates Fas-mediated apoptosis at two different levels: by regulating the expression level of Fas, and by regulating the expression level of c-Flip, an endogenous antagonist of caspase-8. The extracellular signal-regulated kinase (Erk) cascade functions as a survival pathway in adherent cells by regulating c-Flip expression. We further show that detachment-induced cell death, or anoikis, itself results from activation of the Fas pathway by its ligand, Fas-L. Fas-L/Fas interaction, Fas-FADD complex formation, and caspase-8 activation precede the bulk of anoikis in endothelial cells, and inhibition of any of these events blocks anoikis. These studies identify matrix attachment as a survival factor against death receptor-mediated apoptosis and provide a molecular mechanism for anoikis and previously observed Fas resistance in endothelial cells.

Anoikis↗
PubMed2001

Interaction of endostatin with integrins implicated in angiogenesis.

Endostatin, a fragment of collagen XVIII, is a potent antagonist of angiogenesis and inhibitor of tumor growth in mouse models. At present, the mechanism of action of endostatin is unknown. We show here that recombinantly produced human endostatin interacts with alpha(5)- and alpha(v)-integrins on the surface of human endothelial cells. We further demonstrate that the endostatin-integrin interaction is of functional significance in vitro, as we found that immobilized endostatin supports endothelial cell survival and migration in an integrin-dependent manner. Soluble endostatin in turn inhibits integrin-dependent endothelial cell functions, such as cell migration. Taken together, these results implicate integrins as potential targets for endostatin function and support the importance of integrins in endothelial cell biology and angiogenesis.

Angiogenesis Inhibitors↗
PubMed2001

Proton spectroscopic imaging shows abnormalities in glial and neuronal cell pools in frontal lobe epilepsy.

PURPOSE: Proton magnetic resonance spectroscopic imaging (1H MRSI) can lateralize the epileptogenic frontal lobe by detecting metabolic ratio abnormalities in frontal lobe epilepsy (FLE). We used 1H MRS to lateralize and localize the epileptogenic focus, and we also sought to characterize further the metabolic abnormality in FLE. METHODS: We measured signals from N-acetyl aspartate (NAA), choline-containing compounds (Cho), and creatine + phosphocreatine (Cr) in the supraventricular brain of 14 patients with frontal or frontoparietal epilepsy and their matched controls. The supratentorial brain also was segmented into gray matter, white matter, and cerebrospinal fluid classes. Regional metabolite alterations were compared with localizing and lateralizing results from other examination modalities and with histology from three patients. RESULTS: Spectroscopy lateralized the epileptogenic focus in 10 patients in agreement with video-EEG and functional imaging. In four patients, spectroscopy showed bilateral, focal metabolic abnormality, whereas video-EEG suggested unilateral or midline abnormality. In the epileptogenic focus, Cho and Cr were increased by 23% and 14%, respectively, and NAA was decreased by 11%, suggesting metabolic disturbances both in the glial and in the neuronal cell pools. Two Taylor dysplasia lesions confirmed by histology and one with radiologic diagnosis showed high Cho and low or normal NAA, whereas two dysembryoplastic neurogenic tumors had normal Cho and low NAA. Contralateral hemisphere NAA/(Cho + Cr) was decreased in FLE, indicating diffusely altered brain metabolism. Segmentation of brain tissue did not reveal atrophic changes in FLE. CONCLUSIONS: Spectroscopy is useful in lateralizing frontoparietal epilepsy and shows promise as a "noninvasive biopsy" in epileptogenic lesions.

Adolescent↗
PubMed2000

The proto-oncogene c-Cbl is a positive regulator of Met-induced MAP kinase activation: a role for the adaptor protein Crk.

Hepatocyte growth factor triggers a complex biological program leading to invasive cell growth by activating the c-Met receptor tyrosine kinase. Following activation, Met signaling is elicited via its interactions with SH2-containing proteins, or via the phosphorylation of the docking protein Gab1, and the subsequent interaction of Gab1 with additional SH2-containing effector molecules. We have previously shown that the interaction between phosphorylated Gab1 and the adaptor protein Crk mediates activation of the JNK pathway downstream of Met. We report here that c-Cbl, which is a Gab1-like docking protein, also becomes tyrosine-phosphorylated in response to Met activation and serves as a docking molecule for various SH2-containing molecules, including Crk. We further show that Cbl is similarly capable of enhancing Met-induced JNK activation, and several lines of experimentation suggests that it does so by interacting with Crk. We also show that both Cbl and Gab1 enhance Met-induced activation of another MAP kinase cascade, the ERK pathway, in a Crk-independent manner. Taken together, our studies demonstrate a previously unidentified functional role for Cbl in Met signaling and suggest that Met utilizes at least two docking proteins, Gab1 and Cbl, to activate downstream signaling pathways. Oncogene (2000) 19, 4058 - 4065.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Engagement of the alpha2beta1 integrin inhibits Fas ligand expression and activation-induced cell death in T cells in a focal adhesion kinase-dependent manner.

T-cell receptor (TCR)-mediated apoptosis, also known as activation-induced cell death (AICD), plays an important role in the control of immune response and in the development of T-cell repertoire. Mechanistically, AICD has been largely attributed to the interaction of Fas ligand (Fas-L) with its cell surface receptor Fas in activated T cells. Signal transduction mediated by the integrin family of cell adhesion receptors has been previously shown to modulate apoptosis in a number of different cell types; in T cells, integrin signaling is known to be important in cellular response to antigenic challenge by providing a co-stimulatory signal for TCR. In this study we demonstrate that signaling via the collagen receptor alpha2beta1 integrin specifically inhibits AICD by inhibiting Fas-L expression in activated Jurkat T cells. Engagement of the alpha2beta1 integrin with monoclonal antibodies or with type I collagen, a cognate ligand for alpha2beta1, reduced anti-CD3 and PMA/ionomycin-induced cell death by 30% and 40%, respectively, and the expression of Fas-L mRNA by 50%. Further studies indicated that the alpha2beta1-mediated inhibition of AICD and Fas-L expression required the focal adhesion kinase FAK, a known component in the integrin signaling pathways. These results suggest a role for the alpha2beta1 integrin in the control of homeostasis of immune response and T-cell development. (Blood. 2000;95:2044-2051)

Apoptosis↗
PubMed1999

Met-induced JNK activation is mediated by the adapter protein Crk and correlates with the Gab1 - Crk signaling complex formation.

Constitutive activation of the Met tyrosine kinase results in transformation of cells of diverse origin. Recent studies have demonstrated a role for the c-Jun N-terminal kinase (JNK) in Met-induced transformation, but little is known about the molecular mechanisms that connect Met to JNK activation. Our studies show that activated Met associates with, and phosphorylates, the docking protein Gab1, which in turn binds to the src homology 2 (SH2)-domain of the adapter protein Crk and recruits Crk to the Met signaling complex. Formation of the Gab1 - Crk complex correlates with Met-induced JNK activation, and mutant forms of Met that fail to induce the complex formation also fail to activate JNK. Importantly, expression of a loss-of-function mutant of Crk severely impairs activation of the JNK pathway by Met. We also show here that Met controls the transcription of the matrix metalloproteinase-1 (MMP-1) gene in carcinoma cells and that this transcriptional regulation occurs in a Crk - JNK-dependent manner through an AP-1 element in the MMP-1 promoter. Taken together, our data implicate the Gab1 - Crk signaling complex in Met-induced JNK activation and suggest that the Gab1 - Crk complex formation may be an important event in regulating the tumorigenic phenotype of Met-transformed cells.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Adaptor proteins Grb2 and Crk couple Pyk2 with activation of specific mitogen-activated protein kinase cascades.

The protein tyrosine kinase Pyk2 acts as an upstream regulator of mitogen-activated protein (MAP) kinase cascades in response to numerous extracellular signals. The precise molecular mechanisms by which Pyk2 activates distinct MAP kinase pathways are not yet fully understood. In this report, we provide evidence that the protein tyrosine kinase Src and adaptor proteins Grb2, Crk, and p130Cas act as downstream mediators of Pyk2 leading to the activation of extracellular signal-regulated kinase (ERK) and c-Jun amino-terminal kinase (JNK). Pyk2-induced activation of Src is necessary for phosphorylation of Shc and p130Cas and their association with Grb2 and Crk, respectively, and for the activation of ERK and JNK cascades. Expression of a Grb2 mutant with a deletion of the amino-terminal Src homology 3 domain or the carboxyl-terminal tail of Sos strongly reduced Pyk2-induced ERK activation, with no apparent effect on JNK activity. Grb2 with a deleted carboxyl-terminal Src homology 3 domain partially blocked Pyk2-induced ERK and JNK pathways, whereas expression of dominant interfering mutants of p130Cas or Crk specifically inhibited JNK but not ERK activation by Pyk2. Taken together, our data reveal specific pathways that couple Pyk2 with MAP kinases: the Grb2/Sos complex connects Pyk2 to the activation of ERK, whereas adaptor proteins p130Cas and Crk link Pyk2 with the JNK pathway.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Comparison of combination therapy with single-drug therapy in early rheumatoid arthritis: a randomised trial. FIN-RACo trial group.

BACKGROUND: The treatment of rheumatoid arthritis should aim at clinical remission. This multicentre, randomised trial with 2-year follow-up sought evidence on the efficacy and tolerability of combination therapy (sulphasalazine, methotrexate, hydroxychloroquine, and prednisolone) compared with treatment with a single disease-modifying antirheumatic drug, with or without prednisolone, in the treatment of early rheumatoid arthritis. METHODS: 199 patients were randomly assigned to two treatment groups. 195 started the treatment (97 received combination and 98 single drug therapy). Single-drug therapy in all patients started with sulphasalazine; in 51 patients methotrexate was later substituted. Oral prednisolone was required by 63 patients. The primary outcome measure was induction of remission. Analyses were intention to treat. FINDINGS: 87 patients in the combination group and 91 in the single-therapy group completed the trial. After a year, remission was achieved in 24 of 97 patients with combination therapy, and 11 of 98 with single-drug therapy (p=0.011). The remission frequencies at 2 years were 36 of 97 and 18 of 98 (p=0.003). Clinical improvement (American College of Rheumatology criteria of 50% clinical response) was achieved after 1 year in 68 (75%) patients with combination therapy, and in 56 (60%) using single-drug therapy (p=0.028), while at the 2-year visit 69 and 57 respectively (71% vs 58%, p=0.058) had clinically improved. The frequencies of adverse events were similar in both treatment groups. INTERPRETATION: Combination therapy was better and not more hazardous than single treatment in induction of remission in early rheumatoid arthritis. The combination strategy as an initial therapy seems to increase the efficacy of the treatment in at least a proportion of patients with early rheumatoid arthritis.

Adult↗
PubMed1999

Cell adhesion regulates the interaction between the docking protein p130(Cas) and the 14-3-3 proteins.

Integrin ligand binding induces a signaling complex formation via the direct association of the docking protein p130(Cas) (Cas) with diverse molecules. We report here that the 14-3-3zeta protein interacts with Cas in the yeast two-hybrid assay. We also found that the two proteins associate in mammalian cells and that this interaction takes place in a phosphoserine-dependent manner, because treatment of Cas with a serine phosphatase greatly reduced its ability to bind 14-3-3zeta. Furthermore, the Cas-14-3-3zeta interaction was found to be regulated by integrin-mediated cell adhesion. Thus, when cells are detached from the extracellular matrix, the binding of Cas to 14-3-3zeta is greatly diminished, whereas replating the cells onto fibronectin rapidly induces the association. Consistent with these results, we found that the subcellular localization of Cas and 14-3-3 is also regulated by integrin ligand binding and that the two proteins display a significant co-localization during cell attachment to the extracellular matrix. In conclusion, our results demonstrate that 14-3-3 proteins participate in integrin-activated signaling pathways through their interaction with Cas, which, in turn, may contribute to important biological responses regulated by cell adhesion to the extracellular matrix.

14-3-3 Proteins↗
PubMed1998

The adaptor protein Crk connects multiple cellular stimuli to the JNK signaling pathway.

c-Jun N-terminal kinases (JNKs) are potently activated by a number of cellular stimuli. Small GTPases, in particular Rac, are responsible for initiating the activation of the JNK pathways. So far, the signals leading from extracellular stimuli to the activation of Rac have remained elusive. Recent studies have demonstrated that the Src homology 2 (SH2)- and Src homology 3 (SH3)-containing adaptor protein Crk is capable of activating JNK when ectopically expressed. We found here that transient expression of Crk induces JNK activation, and this activation was dependent on both the SH2- and SH3-domains of Crk. Expression of p130(Cas) (Cas), a major binding protein for the Crk SH2-domain, also induced JNK activation, which was blocked by the SH2-mutant of Crk. JNK activation by Cas and Crk was effectively blocked by a dominant-negative form of Rac, suggesting for a linear pathway from the Cas-Crk-complex to the Rac-JNK activation. Many of the stimuli that activate the Rac-JNK pathway enhance engagement of the Crk SH2-domain. JNK activation by these stimuli, such as epidermal growth factor, integrin ligand binding and v-Src, was efficiently blocked by dominant-negative mutants of Crk. A dominant-negative form of Cas in turn blocked the integrin-, but not epidermal growth factor - nor v-Src-mediated JNK activation. Together, these results demonstrate an important role for Crk in connecting multiple cellular stimuli to the Rac-JNK pathway, and a role for the Cas-Crk complex in integrin-mediated JNK activation.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Oncogenic forms of Cbl abrogate the anchorage requirement but not the growth factor requirement for proliferation.

Recent studies have demonstrated that Cbl, the 120 kDa protein product of the c-cbl proto-oncogene, becomes tyrosine phosphorylated in response to stimulation of growth factor receptors and upon integrin-mediated cell adhesion. As a result, Cbl forms complexes with SH2 and SH3 domain-containing proteins, pointing to its role in signal transduction. The cellular form of Cbl can be rendered into transforming by naturally occurring or engineered mutations to its amino acid sequence. To gain insight into the mechanisms how oncogenic forms of Cbl render cells tumorigenic and what the function of the cellular Cbl might be, we have undertaken an analysis of NIH3T3 cells transfected with wild-type and oncogenic forms of Cbl. We demonstrate that unlike cellular Cbl, the mutant forms of Cbl are tyrosine phosphorylated in an adhesion-independent manner and interact with and activate SH2-containing signaling molecules in both suspended and adherent cells. Our data further show that oncogenic forms of Cbl induce anchorage-independent but serum-dependent growth. These results support the view that transformation by oncogenic forms of Cbl results from constitutive activation of integrin-dependent, rather than growth factor-dependent signaling events and, as a corollary, suggest that cellular Cbl might be a functionally important mediator of integrin signaling.

3T3 Cells↗
PubMed1998

CAS/Crk coupling serves as a "molecular switch" for induction of cell migration.

Carcinoma cells selected for their ability to migrate in vitro showed enhanced invasive properties in vivo. Associated with this induction of migration was the anchorage-dependent phosphorylation of p130CAS (Crk-associated substrate), leading to its coupling to the adaptor protein c-CrkII (Crk). In fact, expression of CAS or its adaptor protein partner Crk was sufficient to promote cell migration, and this depended on CAS tyrosine phosphorylation facilitating an SH2-mediated complex with Crk. Cytokine-stimulated cell migration was blocked by CAS lacking the Crk binding site or Crk containing a mutant SH2 domain. This migration response was characterized by CAS/Crk localization to membrane ruffles and blocked by the dominant-negative GTPase, Rac, but not Ras. Thus, CAS/Crk assembly serves as a "molecular switch" for the induction of cell migration and appears to contribute to the invasive property of tumors.

Animals↗
PubMed1998

Extracellular signal-regulated kinase and c-Jun NH2-terminal kinase activation by mechanical stretch is integrin-dependent and matrix-specific in rat cardiac fibroblasts.

Integrins, which connect the cytoskeleton to the extracellular matrix and mediate a variety of signaling cascades, may transduce mechanical stimuli into biochemical signals. We studied integrin- and matrix-dependent activation of extracellular signal-regulated kinase (ERK2), c-Jun NH2-terminal kinase (JNK1), and p38 in response to 4% static biaxial stretch in rat cardiac fibroblasts. ERK2 and JNK1, but not p38, were rapidly activated by stretch when the fibroblasts were allowed to synthesize their own matrices. When the cells were limited to specific matrix substrates, ERK2 and JNK1 were differentially activated: ERK2 was only activated when the cells were plated on fibronectin, while JNK1 was activated when the cells were plated on fibronectin, vitronectin, or laminin. Plating cells on collagen before stretching did not activate either kinase. Adhesion to all matrices was integrin-dependent because it could be blocked by inhibitors of specific integrins. ERK2 activation could be blocked with a combination of anti-alpha4 and -alpha5 antibodies and an arginine-glycine-aspartic acid (RGD) peptide, while the antibodies or peptide used separately failed to block ERK2 activation. This result suggests that at least two integrins, alpha4beta1 and an RGD-directed, non-alpha5beta1 integrin, activate ERK2 in response to mechanical stimulation. Activation of JNK1 could not be blocked with the inhibitors, suggesting that an RGD-independent integrin or integrins other than alpha4beta1 can activate JNK1 in cells adherent to fibronectin. This study demonstrates that integrins act as mechanotransducers, providing insight into potential mechanisms for in vivo responses to mechanical stimuli.

Animals↗
PubMed1997

Epidermal growth factor modulates tyrosine phosphorylation of p130Cas. Involvement of phosphatidylinositol 3'-kinase and actin cytoskeleton.

Epidermal growth factor (EGF) treatment of Rat-1 cells expressing human EGF receptor results in the modification of the tyrosine phosphorylation of the p130 Crk-associated substrate (Cas), a novel signaling molecule residing in focal adhesions. At low, mitogenic concentrations (<10 ng/ml), EGF treatment induced a rapid and transient tyrosine phosphorylation of Cas and promoted the formation of a Cas-adapter protein Crk complex in intact cells. The increase in tyrosine phosphorylation of Cas paralleled an increase in the cellular content of actin stress fibers and occurred via a pathway that depended on the integrity of the cytoskeleton. Further, phosphatidylinositol 3'-kinase activity was found to be required for the EGF-stimulated Cas phosphorylation and actin polymerization. At high concentrations (>30 ng/ml), EGF treatment resulted in the tyrosine dephosphorylation of Cas in a time-dependent manner with a concomitant decrease in the length and number of actin stress fibers. Thus, Cas exhibits an unusual bell-shaped dose-response curve in response to EGF stimulation. These results demonstrate a novel signaling role for EGF in inducing changes in tyrosine phosphorylation of Cas and Cas-Crk complex formation and suggest that Cas could be a signaling component in EGF-mediated signal transduction.

Actins↗