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Huntington's disease is a neurodegenerative disorder caused by a CAG repeat expansion in exon 1 of the huntingtin gene. Striatal projection neurons are mainly affected, leading to motor symptoms, but molecular mechanisms involved in their vulnerability are not fully characterized. Here, we show that eIF4E binding protein (4E-BP), a protein that inhibits translation, is inactivated in Huntington's disease striatum by increased phosphorylation. Accordingly, we detected aberrant de novo protein synthesis. Proteomic characterization indicates that translation specifically affects sets of proteins as we observed upregulation of ribosomal and oxidative phosphorylation proteins and downregulation of proteins related to neuronal structure and function. Interestingly, treatment with the translation inhibitor 4EGI-1 prevented R6/1 mice motor deficits, although corticostriatal long-term depression was not markedly changed in behaving animals. At the molecular level, injection of 4EGI-1 normalized protein synthesis and ribosomal content in R6/1 mouse striatum. In conclusion, our results indicate that dysregulation of protein synthesis is involved in mutant huntingtin-induced striatal neuron dysfunction.

Ribosomes execute the transcriptional program in every cell. Critical to sustain nearly all cellular activities, ribosome biogenesis requires the translation of ~200 factors of which 80 are ribosomal proteins (RPs). As ribosome synthesis depends on RP mRNA translation, a priority within the translatome architecture should exist to ensure the preservation of ribosome biogenesis capacity, particularly under adverse growth conditions. Here, we show that under critical metabolic constraints characterized by mTOR inhibition, LARP1 complexed with the 40S subunit protects from ribophagy the mRNAs regulon for ribosome biogenesis and protein synthesis, acutely preparing the translatome to promptly resume ribosomes production after growth conditions return permissive. Characterizing the LARP1-protected translatome revealed a set of 5′TOP transcript isoforms other than RPs involved in energy production and in mitochondrial function, among other processes, indicating that the mTOR-LARP1-5′TOP axis acts at the translational level as a primary guardian of the cellular anabolic capacity.

Objectives: The goal of this study was to assess mitochondrial function, energy and purine metabolism, protein synthesis machinery from the nucleolus to the ribosome, inflammation, and expression of newly identified ectopic olfactory and taste receptors in the frontal cortex of typical cases of Dementia with Lewy Bodies (DLB) and cases with rapid clinical course (rpDLB: 2 years or less) compared with middle-aged non-affected individuals, in order to learn about the biochemical abnormalities underlying Lewy body pathology. Methods: RT-qPCR, mitochondrial enzymatic assays, and analysis of β-amyloid, tau and synuclein species were used. Results: The main alterations in DLB and rpDLB, which are more marked in the rapidly progressive forms, include: i) deregulated expression of several mRNAs and proteins of mitochondrial subunits, and reduced activity of complexes I, II, III and IV of the mitochondrial respiratory chain; ii) reduced expression of selected molecules involved in energy metabolism and increased expression of enzymes involved in purine metabolism; iii) abnormal expression of nucleolar proteins, rRNA18S, genes encoding ribosomal proteins and initiation factors of the transcription at the ribosome; iv) discrete inflammation; and v) marked deregulation of brain olfactory and taste receptors (ORs and TASRs, respectively). Severe mitochondrial dysfunction involving activity of four complexes, minimal inflammatory responses, and dramatic altered expression of ORs and TASRs discriminate DLB from Alzheimer’s disease. Altered solubility and aggregation of α-synuclein, increased β-amyloid bound to membranes and absence of soluble tau oligomers are common in DLB and rpDLB. Low levels of soluble β-amyloid are found in DLB. However, increased soluble β-amyloid 1-40 and β-amyloid 1-42, and increased TNFα mRNA and protein expression, distinguish rpDLB. Conclusions: Molecular alterations in frontal cortex in DLB involve key biochemical pathways such as mitochondria and energy metabolism, protein synthesis, purine metabolism, among others and are accompanied by discrete innate inflammatory response.Rapid DLB can be distinguished from DLB by increased levels of β-amyloid species and TNF-α mRNA brain expression, being both factors harmful to nerve cells

The correct folding and assembly of newly synthesized secretory proteins are monitored by the protein quality control system of the endoplasmic reticulum (ER). Through interactions with chaperones such as the binding protein (BiP) and other folding helpers, quality control favors productive folding and sorts for degradation defective proteins. A major route for quality control degradation identified in yeast, plants, and animals is constituted by retrotranslocation from the ER to the cytosol and subsequent disposal by the ubiquitin/proteasome system, but alternative routes involving the vacuole have been identified in yeast. In this study, we have studied the destiny of sGFP418, a fusion between a secretory form of GFP and a domain of the vacuolar protein phaseolin that is involved in the correct assembly of phaseolin and in BiP recognition of unassembled subunits. We show that sGFP418, despite lacking the phaseolin vacuolar sorting signal, is delivered to the vacuole and fragmented, in a process that is inhibited by the secretory traffic inhibitor brefeldin A. Moreover, a fusion between GFP and a domain of the maize storage protein gamma-zein involved in zein polymerization also undergoes post-translational fragmentation similar to that of sGFP418. These results show that defective secretory proteins with permanently exposed sequences normally involved in oligomerization can be delivered to the vacuole by secretory traffic. This strongly suggests the existence of a plant vacuolar sorting mechanism devoted to the disposal of defective secretory proteins.

Data from different laboratories have recently indicated that Cup is a multi-functional protein acting both during Drosophila ovary development and early embryogenesis. Cup directly and/or indirectly affects the activity of different mRNAs and proteins to achieve a broad range of biological functions: (1) Cup interacts with Nanos to promote maintenance and survival of the female germ-line stem cells; (2) it binds eIF4E and 3'-UTR-bound factors to repress translation of oskar and nanos mRNAs; (3) it interacts genetically with eIF4E to control translation initiation during ovary development and growth; (4) it may play a role in the control of the phosphorylation status of eIF4E within the developing ovary; finally, (5) it possesses nucleo-cytoplasmic shuttling properties thus pointing to a still uncharacterized function in the cell nucleus. A multi-disciplinary approach, ranging from genetics to proteomics, will be required to shed light on the diverse molecular mechanisms involving Cup and the growing family of its specific interactors.

In Drosophila , the product of the fs (2)cup gene (Cup) is known to be crucial for diverse aspects of female germ-line development. Its functions at the molecular level, however, have remained mainly unexplored. Cup was found to directly associate with eukaryotic translation initiation factor 4E (eIF4E). In this report, we show that Cup is a nucleocytoplasmic shuttling protein and that the interaction with eIF4E promotes retention of the Cup protein in the cytoplasm. Cup is required for the correct accumulation and localization of eIF4E within the posterior cytoplasm of developing oocytes. We furthermore show that cup and eIF4E interact genetically, because a reduction in the level of eIF4E activity deteriorates the development and growth of ovaries bearing homozygous cup mutant alleles. Our results reveal a crucial role for the Cup–eIF4E complex in ovary-specific developmental programs.

Secretory proteins are first inserted cotranslationally into the endoplasmic reticulum (ER) and then transported through the secretory pathway to the cell surface or to inner hydrolytic compartments in a traffic process that is mediated mostly by the Golgi complex. Addition of the oligosaccharide