A replacement of proline with leucine at position 132 of the receptor for parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP), i.e., PTH-R, has been discovered in human Blomstrand's lethal chondrodysplasia. As skeletal deformities in this type of chondrodysplasia appear to compromise the receptor binding to its ligands, we examined the possibility that rat PTH-R carrying P132L mutation (PTH-RP132L) would result in abnormal intracellular localization. Osteoblastic MC3T3-E1 cells were transfected with expression vectors containing cDNAs encoding either wild-type PTH-R or mutant PTH-RP132L. The cells expressing the wild-type PTH-R produced a receptor protein with a molecular mass of 66.3 kDa, which localized its immunoreactivity mainly on the cell surfaces. In contrast, the PTH-RP132L was hardly detected on the cell surfaces, but accumulated within the rough-surfaced endoplasmic reticulum. Consistent with this localization, the cells expressing the mutant receptor failed to generate cyclic AMP in response to PTH. Furthermore, a remarkably weaker intensity of the 66.3 kDa band compared with the wild-type counterpart suggests that PTH-RP132L is prone to degradation in the transfected cells. In summary, these findings indicate that defective transport of PTH-RP132L to the cell surface would be a molecular basis for Blomstrand's chondrodysplasia.
Claudins are transmembrane proteins and major constitutes of tight junctions, and participate in the paracellular barrior and cellular connecting functions. They have been shown to be differentially regulated in malignant tumors and play a role in carcinogenesis and tumor progression. Recent studies have shown changes in expression of claudins during tumorigenesis. However, a causal relationship between claudin expression and cancer recurrent status has not been established. In this study, we examined 54 esophageal cancer cases to assess immunohistochemical expression patterns of claudin-1. Eleven (20.4%) of 54 cases had negative immunostaining for claudin-1. Decreased expression of claudin-1 was statistically correlated with recurrence status (P = 0.018). The cases with lymphatic vessel permeation showed reduced expression patterns of claudin-1 (P = 0.033). Decreased expression of claudin-1 was also correlated with short diseasefree survival (P = 0.0003) and overall survival (P = 0.0045). The results indicated that claudin-1 expression was correlated with the recurrence status and poor prognosis in esophageal cancer and claudin-1 expression may be a good indicator of recurrence in esophageal cancer.
HGF-like protein (HLP)/macrophage stimulating protein (MSP) is the only structural relative of hepatocyte growth factor (HGF), and is involved in the regulation of peripheral macrophage activation. However, the actions of HLP in microglia, a species of macrophage in the nervous system, which is closely involved in the neural degeneration and regeneration, is not yet understood. This study found that Ron, the receptor for HLP, is expressed in primary microglia using RT-PCR, immunocytochemical staining and Western blotting, and, thus, sought to elucidate the function of HLP on the primary microglia. HLP promoted microglial migration without affecting cell survival and proliferation. Furthermore, real-time quantitative RT-PCR analysis revealed that HLP greatly increased the mRNA of inflammatory cytokines, including IL-6 and GM-CSF, and iNOS. These findings provide the first evidence that HLP has the potential to modulate inflammatory actions of microglia, which proposes novel aspects for the process of degeneration and/or regeneration of the brain.
The exocyst is an octameric complex involved in docking or tethering of secretory vesicles to fusion sites of the plasma membrane. Sec6 is the core subunit of the exocyst complex. Here we identify an isoform of Sec6, deposited as Exocyst complex component 3-like (Exoc3l) in the database, by in silico screening using rat Sec6 as a probe. The amino acid sequence of Exoc3l has 31% identity and 53% similarity with that of Sec6. RT-PCR analysis reveals that Exoc3l is expressed in insulin-secreting MIN6 cells as well as in various tissues including pancreatic islets and brain. In co-immunoprecipitation experiments, Exoc3l was found to interact with Sec5, Sec8, and Sec10, all of which are binding partners of Sec6 in the exocyst complex. Furthermore, overexpression of a deletion mutant of Exoc3l in MIN6 cells suppressed glucose-stimulated secretion. These results suggest that Exoc3l is involved in regulated exocytosis of insulin granules.
Circadian rhythm pervades in many aspects of the biological processes including basic cellular functions. Here we examined the circadian gene expression of two forms of 90 kDa heat shock proteins referred to HSP86 and HSP84 in the mouse suprachiasmatic nucleus, the circadian center. In both light-dark, and constant dark conditions, Hsp86 mRNA showed an overt circadian rhythm showing a peak at (subjective) night and a trough at (subjective) day. Hsp84 mRNA also showed the similar expression profile, but the amplitude was weaker. These results indicate that gene expression of molecular chaperone such as Hsp86 and Hsp84 are regulated by the circadian clock.
Recent studies have found alterations to clock genes in several forms of cancer. Period (Per) gene plays an important role in the circadian system, the cell cycle, the induction of apoptosis, and DNA damage. However, the functions of Per in pancreatic cancer have not yet been elucidated. Here, we show that tumor necrosis factor-α (TNF-α) suppressed the expression of both Per1 and Per3 in MIA-PaCa2 cells, a human pancreatic cancer cell line. The levels of these proteins were 10% lower in the cells treated with 10 ng/mL TNF-α. Cell proliferation showed a 15%, 14%, and 16% decrease at 0.4, 2.0, and 10 ng/mL of TNF-α, respectively. In MTS-assays, MIA-PaCa2 cells transfected with siRNA against Per1 showed a 19% reduction in proliferation. However, the knockdown of Per3 did not significantly inhibit cell proliferation. The results suggest Per1 to be involved in the inhibition of the proliferation of MIA-PaCa2 cells by TNF-α.
We investigated the presence of EP1 receptor in the urothelium and its role in micturition reflex by examining the effect of intravesical administration of prostaglandin E2 (PGE2), an EP1 agonist (ONO-DI-004), acetic acid, and capsaicin. Age-matched EP1-KO mice and C57BL/6 wild-type (WT) mice were used. Western blots and standard immunohistochemical procedures were performed. Cystometrygram (CMG) was performed without anesthesia in a restraining cage. ATP release from the cultured urothelium cells was performed using luciferin-luciferase luminometry. The EP1 receptor was found to be present in the urothelium. In WT mice, PGE2 infusion shortened the intercontraction interval (ICI) in a dose-dependent fashion; however, it did not alter the ICI in EP1-KO mice. The EP1 agonist significantly shortened the ICI in WT mice, but not in EP1-KO mice. Acetic acid and capsaicin shortened the ICI in both WT mice and EP1-KO mice. EP1 agonist, PGE2 and capsaicin provoked ATP release from cultured urothelial cells. These results suggest that EP1 receptor was present in bladder urothelium, and could be activated by PGE2 to release ATP. EP1 receptor in urothelium might be important for reflex voiding in pathological conditions.
Various inflammatory mediators released from antigen-activated mast cells are considered to play a key role in the pathogenesis of food allergy. The aim of the present study was to determine the mechanisms underlying the antigen-induced anaphylactic responses in the rat colons. Wistar rats were sensitized by intraperitoneal injection of ovalbumin (OVA). The contractilities of isolated proximal colons of the sensitized rats were studied in the organ bath. OVA challenges of sensitized tissues induced prolonged contractile responses. The antigen-induced contractions were greatly reduced by mast cell stabilizer doxantrazole (10 μM). However, the contractions were resistant to histamine H1 receptor antagonist and prostaglandin D2 receptor antagonist. In contrast, non-selective cyclooxygenase (COX) inhibitor indomethacin (1 μM) significantly reduced the contractions by 61.0%. Furthermore, selective COX-1 inhibitor FR122047 (10 μM) as well as selective COX-2 inhibitor NS-398 (10 μM) significantly inhibited the contractions by 50.1% and 50.3%, respectively. Nevertheless, the transcript levels of COX-2 as well as COX-1 were not upregulated by OVA in the proximal colons of the sensitized rats. The present results indicate that de novo arachidonic acid metabolites synthesis by constitutive COX-1 as well as constitutive COX-2 within mast cells contribute to the altered smooth muscle contractilities in the colons under the anaphylactic condition.