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J Sai

Publications and source records attributed to J Sai.

8 recordsLinked to original sources
PubMed2001

Phosphorylation-independent association of CXCR2 with the protein phosphatase 2A core enzyme.

Protein phosphatase 2A (PP2A) is postulated to be involved in the dephosphorylation of G protein-coupled receptors. In the present study, we demonstrate that the carboxyl terminus of CXCR2 physically interacts with the PP2A core enzyme, a dimer formed by PP2Ac and PR65, but not with the PP2Ac monomer, suggesting direct interaction of the receptor with PR65. The integrity of a sequence motif in the C terminus of CXCR2, KFRHGL, which is conserved in all CC and CXC chemokine receptors, is required for the receptor binding to the PP2A core enzyme. CXCR2 co-immunoprecipitates with the PP2A core enzyme in HEK293 cells and in human neutrophils. Overexpression of dominant negative dynamin 1 (dynamin 1 K44A) in CXCR2-expressing cells blocks the receptor association with the PP2A core enzyme, and an internalization-deficient mutant form of CXCR2 (I323A,L324A) also exhibits impaired association with the PP2A core enzyme, suggesting that the receptor internalization is required for the receptor binding to PP2A. A phosphorylation-deficient mutant of CXCR2 (331T), which has previously been shown to undergo internalization in HEK293 cells, binds to an almost equal amount of the PP2A core enzyme in comparison with the wild-type CXCR2, suggesting that the interaction of the receptor with PP2A is phosphorylation-independent. The dephosphorylation of CXCR2 is reversed by treatment of the cells with okadaic acid. Moreover, pretreatment of the cells with okadaic acid increases basal phosphorylation of CXCR2 and attenuates CXCR2-mediated calcium mobilization and chemotaxis. Taken together, these data indicate that PP2A is involved in the dephosphorylation of CXCR2. We postulate that this interaction results from direct binding of the regulatory subunit A (PR65) of PP2A to the carboxyl terminus of CXCR2 after receptor sequestration and internalization.

Amino Acid Sequence↗
PubMed1999

Different circadian oscillators control Ca(2+) fluxes and lhcb gene expression.

Circadian biological clocks control many biological events, but the pathways by which these events are controlled are largely unknown. Based on a model suggesting that cytosolic-free calcium levels control the expression of the Lhcb gene in plants, we tested whether the circadian oscillation of free calcium is responsible for driving the rhythm of Lhcb expression. We found that these rhythms free-run with different periods in tobacco seedlings in constant conditions. Moreover, robust oscillations of Lhcb promoter activity continued in undifferentiated tobacco calli in the absence of Ca(2+) oscillations. Therefore, these two circadian rhythms are not linked hierarchically. These data provide evidence for separate circadian pacemakers controlling molecular events in plants.

Aequorin↗
PubMed1998

Imaging of small pancreatic ductal adenocarcinoma.

Symptoms and laboratory studies provide only limited assistance in the diagnosis of small pancreatic carcinomas. Ultrasound and computed tomography are best suited for screening small pancreatic carcinomas because of their ease and accuracy. When findings of ultrasound and computed tomography suggest small pancreatic carcinomas, MR cholangiopancreatography and endoscopic ultrasound should be indicated. Both techniques can show very small tumors. Follow-up of 77 patients with pancreatic carcinoma in whom the tumor was resected showed a 100% 5-year survival rate of patients with tumor limited to the duct epithelium. The majority of these tumors were <1 cm. These tumors are considered early pancreatic carcinoma.

Adenocarcinoma↗
PubMed1998

[Clinical evaluation of MRCP].

Recently, MRCP can be obtained with good spacial resolution within a few seconds using half fourier fast spin echo technique. From July 1995 to August 1997, 1000 patients suspected of having pancreatobiliary diseases were examined with MRCP. MRCP was performed with 1.5 T scanner using Fast Asymmetric Spin Echo sequence (FASE). Satisfactory images of the main pancreatic duct were obtained in 98%, of Santorini's duct in 90%, and of uncinate process branch in 83%. Pancreas divism was accurately diagnosed. In the patients with pancreatic ductal adenocarcinomas, MRCP depicted stenosis and proximal dilatation of the main pancreatic duct in 89%, and in the remaining patients no abnormalities were seen in the main pancreatic ducts because tumors were limited to side branches or Santorini's duct or distal end of the tail of the pancreas. Diagnosis of small pancreatic carcinomas (smallest lesion measured 10 mm in diameter) were feasible. In the patients with intraductal papillary neoplasms, dilatation of the main pancreatic duct and cystic dilatation of side branches were depicted, and polypoid lesions were detectable with source images. In the patients with serous cystadenomas, accumulation of the microcysts were visualized. In the patients with chronic pancreatitis, dilatation and stenosis of the main pancreatic duct, as well as side branch dilatation was depicted despite overestimation of the extent of the stenosis. Stones in the main pancreatic duct were well visualized as intraductal filling defects. In conclusion, MRCP is an effective imaging technique in the diagnosis of various pancreatic diseases.

Biliary Tract↗
PubMed1998

[Cystic lesions of the pancreas].

The number of the literature and classification of the cystic pancreatic diseases is increasing recently. We describe MR cholangiopancreatography (MRCP) findings of the cystic pancreatic diseases according to the clinical oriented classification. Intraductal papillary tumor, mucinous cystadenoma and serous cystadenoma showed characteristic MRCP findings. However small non-neoplastic true cysts are difficult to differentiate from cystic tumors even by MRCP.

Acute Disease↗
PubMed1995

Nucleotide sequence of maize dwarf mosaic virus capsid protein gene and its expression in Escherichia coli.

The 3'-terminal 1,279 nucleotide sequence of maize dwarf mosaic virus (MDMV) genome has been determined. This sequence contains an open reading frame of 1,023 nucleotides and a 3'-non-coding region of 256 nucleotides. The open reading frame includes all of the coding regions for the viral capsid protein (CP) and part of the viral nuclear inclusion protein (NIb). The predicted viral CP consists of 313 amino acid residues with a calculated molecular weight of 35,400. The amino acid sequence of the viral CP derived from MDMV cDNA shows about 47%-54% homology to that of 4 other potyviruses. The viral CP gene was constructed in frame with the lacZ gene in pUC19 plasmid and expressed in E. coli cells. The fusion polypeptide positively reacted in Western blot with an antiserum prepared against the native viral CP.

Amino Acid Sequence↗