Huntingtin turnover: modulation of huntingtin degradation by cAMP-dependent protein kinase A (PKA) phosphorylation of C-HEAT domain Ser2550.

Huntington's disease (HD) is a neurodegenerative disorder caused by an inherited unstable HTT CAG repeat that expands further, thereby eliciting a disease process that may be initiated by polyglutamine-expanded huntingtin or a short polyglutamine-product. Phosphorylation of selected candidate residues is reported to mediate polyglutamine-fragment degradation and toxicity. Here to support the discovery of phosphosites involved in the life-cycle of (full-length) huntingtin, we employed mass spectrometry-based phosphoproteomics to systematically identify sites in purified huntingtin and in the endogenous protein by proteomic and phosphoproteomic analyses of members of an HD neuronal progenitor cell panel. Our results bring total huntingtin phosphosites to 95, with more located in the N-HEAT domain relative to numbers in the Bridge and C-HEAT domains. Moreover, phosphorylation of C-HEAT Ser2550 by cAMP-dependent protein kinase (PKA), the top hit in kinase activity screens, was found to hasten huntingtin degradation, such that levels of the catalytic subunit (PRKACA) were inversely related to huntingtin levels. Taken together, these findings highlight categories of phosphosites that merit further study and provide a phosphosite kinase pair (pSer2550-PKA) with which to investigate the biological processes that regulate huntingtin degradation and thereby influence the steady state levels of huntingtin in HD cells.

A systematic review of the timing of intubation in patients with traumatic brain injury: pre-hospital versus in-hospital intubation.

PURPOSE: The objective of this systematic review was to examine current evidence on the risks versus benefit of pre-hospital intubation when compared with in-hospital intubation in adult patients with traumatic brain injuries. METHODS: We conducted electronic searches of PubMed, Medline, Embase, CIANHL and the Cochrane library up to March 2021. Data extracted compared mortality, length of hospital and intensive care stay, pneumonia and functional outcomes in traumatic brain injured patients undergoing pre-hospital intubation versus in-hospital intubation. The risk of bias was assessed using the Grading of Recommendations Assessment, Development and Evaluation. RESULTS: Ten studies including 25,766 patients were analysed. Seven were retrospective studies, two prospective cohort studies and one randomised control study. The mean mortality rate in patients who underwent pre-hospital intubation was 44.5% and 31.98% for in-hospital intubation. The odds ratio for an effect of pre-hospital intubation on mortality ranged from 0.31 (favouring in-hospital intubation) to 3.99 (favouring pre-hospital). The overall quality of evidence is low; however, the only randomised control study showed an improved functional outcome for pre-hospital intubation at 6 months. CONCLUSIONS: The existing evidence does not support widespread pre-hospital intubation in all traumatic brain injured patients. This does not, however, contradict the need for the intervention when there is severe airway compromise; instead, it must be assessed by experienced personnel if a time critical transfer to hospital is more advantageous. Favourable neurological outcomes highlighted by the randomised control trial favours pre-hospital intubation, but further research is required in this field.

Polyglutamine-Expanded Huntingtin Exacerbates Age-Related Disruption of Nuclear Integrity and Nucleocytoplasmic Transport.

Onset of neurodegenerative disorders, including Huntington's disease, is strongly influenced by aging. Hallmarks of aged cells include compromised nuclear envelope integrity, impaired nucleocytoplasmic transport, and accumulation of DNA double-strand breaks. We show that mutant huntingtin markedly accelerates all of these cellular phenotypes in a dose- and age-dependent manner in cortex and striatum of mice. Huntingtin-linked polyglutamine initially accumulates in nuclei, leading to disruption of nuclear envelope architecture, partial sequestration of factors essential for nucleocytoplasmic transport (Gle1 and RanGAP1), and intranuclear accumulation of mRNA. In aged mice, accumulation of RanGAP1 together with polyglutamine is shifted to perinuclear and cytoplasmic areas. Consistent with findings in mice, marked alterations in nuclear envelope morphology, abnormal localization of RanGAP1, and nuclear accumulation of mRNA were found in cortex of Huntington's disease patients. Overall, our findings identify polyglutamine-dependent inhibition of nucleocytoplasmic transport and alteration of nuclear integrity as a central component of Huntington's disease.