Hisashi Kurata

The Ras-Mitogen-activated Protein Kinase Pathway Is Critical for the Activation of Matrix Metalloproteinase Secretion and the Invasiveness in v-crk-transformed 3Y1

To search for the intracellular signaling pathway critical for the secretion of matrix metalloproteinases (MMP), we studied the effects of dominant negative Ras (S17N Ras) and dominant negative MEK1 (MEK1AA) expression in v-crk-transformed 3Y1. Expression of either S17N Ras or MEK1AA dramatically suppressed the augmented secretion of MMP-2 and MMP-9 in v-crk-transfected 3Y1. Similarly, a Ras farnesyltransferase inhibitor, manumycin A, and a MEK1 inhibitor, U0126, suppressed MMP secretion in a dose-dependent manner, whereas a PI3 kinase inhibitor, wortmannin, could not. In addition, the suppression of MMP secretion by S17N Ras showed good correlation with the inhibition of in vitro invasiveness of the cells. In contrast, expression of dominant negative C3G did not suppress MMP secretion, although it substantially blocked the c-Jun N-terminal kinase activation. Taken together, the Ras-MEK1 pathway, but not the C3G-JNK pathway, seems to play a key role in the activation of MMP secretion and, hence, the invasiveness of v-crk-transformed cells.

Peritonitis is still an important factor for withdrawal from peritoneal dialysis therapy in the Tokai area of Japan

BackgroundIn Japan, the population of patients on peritoneal dialysis (PD) is <4% of the total number of patients with end-stage renal disease. Few systemic analyses have examined why the number of PD patients has not increased in Japan. We organized a registry to analyze PD patients and retrospectively investigated 561 PD patients (about 5% of all Japanese PD patients) from 13 hospitals in the Tokai area for 3 years from 2005.MethodsWe investigated background, physical status, laboratory data, status of PD therapy, and the occurrence of PD-related complications, and analyzed reasons for withdrawal from PD.ResultsNutrition did not change significantly during our observation. Urinary volume showed continued decreases after the introduction period. In contrast, PD fluid demand and ultrafiltration volume were significantly increased. For calcium metabolism, multiple phosphate binders were required after the second year of PD therapy. Early drop-out within 3 years after starting PD therapy comprised 50.9% of total withdrawals, with PD-related peritonitis as the most common reason, mainly caused by Gram-positive organisms. Incidence of peritonitis was 42.8 months/patient. Culture-negative results were obtained for 32% of peritonitis cultures. Diabetes affects the prognosis of PD therapy, but not the incidence of peritonitis.ConclusionWe examined clinical status over 3 years in the Tokai area. The results suggest that the incidence of peritonitis needs to be decreased to prevent early withdrawal of PD patients. Education systems to decrease the incidence of peritonitis and techniques to decrease culture-negative results might be important for improving the prognosis of peritonitis.

v-Src suppresses SHPS-1 expression via the Ras-MAP kinase pathway to promote the oncogenic growth of cells.

We investigated the effect of cell transformation by v-src on the expression and tyrosine phosphorylation of SHPS-1, a putative docking protein for SHP-1 and SHP-2. We found that transformation by v-src virtually inhibited the SHPS-1 expression at mRNA level. While nontransforming Src kinases including c-Src, nonmyristoylated forms of v-Src had no inhibitory effect on SHPS-1 expression, transforming Src kinases including wild-type v-Src and chimeric mutant of c-Src bearing v-Src SH3 substantially suppressed the SHPS-1 expression. In cells expressing temperature sensitive mutant of v-Src, suppression of the SHPS-1 expression was temperature-dependent. In contrast, tyrosine phosphorylation of SHPS-1 was rather activated in cells expressing c-Src or nonmyristoylated forms of v-Src. SHPS-1 expression in SR3Y1 was restored by treatment with herbimycin A, a potent inhibitor of tyrosine kinase, or by the expression of dominant negative form of Ras. Contrary, active form of Mek1 markedly suppressed SHPS-1 expression. Finally, overexpression of SHPS-1 in SR3Y1 led to the drastic reduction of anchorage independent growth of the cells. Taken together, our results suggest that the suppression of SHPS-1 expression is a pivotal event for cell transformation by v-src, and the Ras-MAP kinase cascade plays a critical role in the suppression.

Molecular cloning and characterization of a novel human gene (NESCA) which encodes a putative adapter protein containing SH3

A full-length cDNA encoding a novel protein was isolated and sequenced from a human placental cDNA library. This cDNA consists of 1990 bp and has a predicted open reading frame encoding 433 amino acids. It possesses an Src homology 3 (SH3) motif, a leucine zipper motif and no catalytic domain, suggesting that it seems to be an adapter protein. PCR-based mapping with both a monochromosomal hybrid panel and radiation hybrid cell panels placed the gene to human chromosome 1q21-22.

Suppression of cell spreading by v-Crk requires Ras-MEK-MAP kinase signaling

We investigated the attachment and spreading of v-Crk-transformed cells, v-Crk3Y1, on fibronectin. Transformation by v-Crk virtually suppressed the spreading, but not the attachment, of cells on fibronectin. This suppression of cell spreading was not correlated with the suppression of integrin α5 and β1 expression. However, the spreading of v-Crk3Y1 on fibronectin was dramatically restored by either expression of dominant-negative Ras or treatment with manumycin A, a Ras farnesyltransferase inhibitor. Moreover, both expression of dominant-negative MEK1 and treatment of cells with U0126, a MEK1 inhibitor, restored the cell spreading of v-Crk3Y1. In contrast, neither treatment with LY294002, a PI3K inhibitor, nor expression of dominant-negative C3G showed no effect on cell spreading on fibronectin. Taken together, our results suggest that, among multiple signaling pathways activated by v-Crk, the Ras-MEK1-MAP kinase cascade plays a pivotal role in the suppression of cell spreading on fibronectin, but C3G and the PI3 kinase do not.