No abstract

Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant neurodegenerative disease characterized by various symptoms including cerebellar ataxia. Recently, several missense mutations in the protein kinase C␥ (␥PKC) gene have been found in different SCA14 families. To elucidate how the mutant ␥PKC causes SCA14, we examined the molecular properties of seven mutant (H101Y, G118D, S119P, S119F, Q127R, G128D, and F643L) ␥PKCs fused with green fluorescent protein (␥PKC-GFP). Wild-type ␥PKC-GFP was expressed ubiquitously in the cytoplasm of CHO cells, whereas mutant ␥PKC-GFP tended to aggregate in the cytoplasm. The insolubility of mutant ␥PKC-GFP to Triton X-100 was increased and correlated with the extent of aggregation. ␥PKC-GFP in the Triton-insoluble fraction was rarely phosphorylated at Thr 514 , whereas ␥PKC-GFP in the Triton-soluble fraction was phosphorylated. Furthermore, the stimulation of the P2Y receptor triggered the rapid aggregation of mutant ␥PKC-GFP within 10 min after transient translocation to the plasma membrane. Overexpression of the mutant ␥PKC-GFP caused cell death that was more prominent than wild type. The cytotoxicity was exacerbated in parallel with the expression level of the mutant. These results indicate that SCA14 mutations make ␥PKC form cytoplasmic aggregates, suggesting the involvement of this property in the etiology of SCA14.

It has been shown that centrally administered neuropeptide Y (NPY) delays gastric emptying. To determine the receptor subtypes of NPY mediating the inhibitory effects on gastric emptying, effects of intracerebroventricular injection of NPY, [Leu31,Pro34]NPY (a Y1 agonist) and NPY-(3-36) (a Y2 agonist) on solid gastric emptying and postprandial antropyloric motility were studied in conscious rats. Intracerebroventricular injection of NPY and NPY-(3-36), but not [Leu31,Pro34] NPY, delayed solid gastric emptying in a dose-dependent manner (0.03-3 nmol). After the feeding (40 min), contractions with low frequency and high amplitude of the antrum were frequently observed, and the peak contraction of the antrum occurred most often 3-6 s before the peak contraction of the pylorus. Intracerebroventricular injection of NPY and NPY-(3-36) (3 nmol), but not [Leu31,Pro34]NPY, significantly reduced antral contractions and the number of antropyloric coordination events. It is suggested that centrally administered NPY impairs postprandial antral contractions and antropyloric coordination via Y2 receptors, resulting in delayed gastric emptying.

Effects of long term (72-h

No abstract

Abstract. We investigated the effects of brefeldin A and ilimaquinone, inhibitors of membrane trafficking, using serotonin transporter (SERT)-expressing COS-7 cells. Both drugs significantly inhibited the serotonin uptake activity of SERT and caused SERT to be retained in the endoplasmic reticulum (ER), indicating that membrane trafficking is an important factor for SERT functional regulation. In agreement with previous reports, a C-terminal-deletion mutant of SERT (SERTΔCT) mostly localized to the ER and completely lacked serotonin uptake activity. To further elucidate the role of the C-terminus of SERT, we investigated whether overexpression of FLAG-tagged SERT C-terminus (FLAG-SERT-CT) affected the serotonin uptake activity and glycosylation of SERT. Interestingly, when concomitantly expressed with full-length FLAG-SERT in COS-7 cells, FLAG-SERT-CT increased the serotonin uptake activity and mature glycosylation of FLAG-SERT. These results indicate that the C-terminal region of SERT plays a crucial role in the functional regulation of SERT via membrane trafficking and glycosylation. In addition, proteasome inhibitors induced apparent ER stress, significantly decreased the serotonin uptake activity and mature glycosylation of SERT and caused SERT to be localized to the ER, suggesting that SERT function would be attenuated via membrane trafficking in pathological states that trigger ER stress.

No abstract

No abstract