A functional Rim101 complex is required for proper accumulation of the Ena1 Na+-ATPase protein in response to salt stress in Saccharomyces cerevisiae.

The maintenance of ionic homeostasis is essential for cell viability, thus the activity of plasma membrane ion transporters must be tightly controlled. Previous studies in Saccharomyces cerevisiae revealed that the proper trafficking of several nutrient permeases requires the E3 ubiquitin ligase Rsp5 and, in many cases, the presence of specific adaptor proteins needed for Rsp5 substrate recognition. Among these adaptor proteins are nine members of the arrestin-related trafficking adaptor (ART) family. We studied the possible role of the ART family in the regulation of monovalent cation transporters. We show here that the salt sensitivity phenotype of the rim8/art9 mutant is due to severe defects in Ena1 protein accumulation, which is not attributable to transcriptional defects. Many components of the Rim pathway are required for correct Ena1 accumulation, but not for the accumulation of other nutrient permeases. Moreover, we observe that strains lacking components of the endosomal sorting complexes required for transport (ESCRT) pathway previously described to play a role in Rim complex formation present similar defects in Ena1 accumulation. Our results show that, in response to salt stress, a functional Rim complex via specific ESCRT interactions is required for the proper accumulation of the Ena1 protein, but not induction of the ENA1 gene.

A "double hit" murine model for schizophrenia shows alterations in the structure and neurochemistry of the medial prefrontal cortex and the hippocampus.

Both alterations in neurodevelopment and aversive experiences during childhood and adolescence seem important risk factors for schizophrenia. Animal models reproducing these alterations mimic some of the symptoms, constituting a valid approach to study the etiopathology of this disorder. Among these models, the perinatal injection of N-methyl-d-aspartate receptor antagonists and the postweaning social isolation rearing are among the most widely used. Our aim is to combine them in a "double hit" model, which should produce a wider spectrum of alterations. Lister Hooded rats have been subjected to a single injection of MK-801 at postnatal day 7 and socially isolated from postweaning to adulthood. These animals presented increased body weight gain and volume reductions in their medial prefrontal cortex (mPFC) and hippocampus. They also showed an increased number of activated pyramidal neurons and alterations in the numbers of parvalbumin and calbindin expressing interneurons in the mPFC. The expressions of the polysialylated form of the neural cell adhesion molecule and GAD67 are decreased in the mPFC. The mRNA level of calbindin was decreased, while that of calretinin was increased in the mPFC. The mRNA level of ERbB4, a gene associated to schizophrenia, was also altered in this region. All these structural and neurochemical alterations, specially in cortical inhibitory circuits, are similar to those found in schizophrenic patients and are more numerous than in each of the single models. Consequently, the present "double hit" model may be a better tool to study the neurobiological basis of schizophrenia and to explore new therapeutic approaches.