McGill University

About: McGill University is a education organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 72688 authors who have published 162565 publications receiving 6966523 citations. The organization is also known as: Royal institution of advanced learning & University of McGill College.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

Abstract: In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Ubiquitin is phosphorylated by PINK1 to activate parkin

Abstract: Ubiquitin, known for its role in post-translational modification of other proteins, undergoes post-translational modification itself; after a decrease in mitochondrial membrane potential, the kinase enzyme PINK1 phosphorylates ubiquitin at Ser 65, and the phosphorylated ubiquitin then interacts with ubiquitin ligase (E3) enzyme parkin, which is also phosphorylated by PINK1, and this process is sufficient for full activation of parkin enzymatic activity. The small protein ubiquitin, familiar for its role in post-translational modification of other proteins by binding to them and regulating their activity or stability, is shown here to be the substrate of the kinase PINK1, which together with the ubiquitin ligase parkin is a causal gene for hereditary recessive Parkinsonism. Noriyuki Matsuda and colleagues show that following a decrease in mitochondrial membrane potential, PINK1 phosphorylates ubiquitin at serine residue 65; the phosphorylated ubiquitin then interacts with parkin, which is also phosphorylated by PINK1. This interaction allows full activation of parkin enzymatic activity, which involves tagging mitochondrial substrates with ubiquitin. PINK1 (PTEN induced putative kinase 1) and PARKIN (also known as PARK2) have been identified as the causal genes responsible for hereditary recessive early-onset Parkinsonism1,2. PINK1 is a Ser/Thr kinase that specifically accumulates on depolarized mitochondria, whereas parkin is an E3 ubiquitin ligase that catalyses ubiquitin transfer to mitochondrial substrates3,4,5. PINK1 acts as an upstream factor for parkin6,7 and is essential both for the activation of latent E3 parkin activity8 and for recruiting parkin onto depolarized mitochondria8,9,10,11,12. Recently, mechanistic insights into mitochondrial quality control mediated by PINK1 and parkin have been revealed3,4,5, and PINK1-dependent phosphorylation of parkin has been reported13,14,15. However, the requirement of PINK1 for parkin activation was not bypassed by phosphomimetic parkin mutation15, and how PINK1 accelerates the E3 activity of parkin on damaged mitochondria is still obscure. Here we report that ubiquitin is the genuine substrate of PINK1. PINK1 phosphorylated ubiquitin at Ser 65 both in vitro and in cells, and a Ser 65 phosphopeptide derived from endogenous ubiquitin was only detected in cells in the presence of PINK1 and following a decrease in mitochondrial membrane potential. Unexpectedly, phosphomimetic ubiquitin bypassed PINK1-dependent activation of a phosphomimetic parkin mutant in cells. Furthermore, phosphomimetic ubiquitin accelerates discharge of the thioester conjugate formed by UBCH7 (also known as UBE2L3) and ubiquitin (UBCH7∼ubiquitin) in the presence of parkin in vitro, indicating that it acts allosterically. The phosphorylation-dependent interaction between ubiquitin and parkin suggests that phosphorylated ubiquitin unlocks autoinhibition of the catalytic cysteine. Our results show that PINK1-dependent phosphorylation of both parkin and ubiquitin is sufficient for full activation of parkin E3 activity. These findings demonstrate that phosphorylated ubiquitin is a parkin activator.

Sustained product innovation in large, mature organizations: Overcoming innovation-to-organization problems.

Abstract: We examined problems with sustained product innovation in 15 firms that averaged 96 years of age, 54,000 employees, and $9.4 billion in annual revenues. Findings reveal that the inability to connec...

Pathways of chaperone-mediated protein folding in the cytosol

Abstract: Cells are faced with the task of folding thousands of different polypeptides into a wide range of conformations. For many proteins, the folding process requires the action of molecular chaperones. In the cytosol of prokaryotic and eukaryotic cells, molecular chaperones of different structural classes form a network of pathways that can handle substrate polypeptides from the point of initial synthesis on ribosomes to the final stages of folding.

Development of a multiple sclerosis functional composite as a clinical trial outcome measure

Abstract: The primary clinical outcome measure for evaluating multiple sclerosis in clinical trials has been Kurtzke's expanded disability status scale (EDSS). New therapies appear to favourably impact the course of multiple sclerosis and render continued use of placebo control groups more difficult. Consequently, future trials are likely to compare active treatment groups which will most probably require increased sample sizes in order to detect therapeutic efficacy. Because more responsive outcome measures will be needed for active arm comparison studies, the National Multiple Sclerosis Society's Advisory Committee on Cinical Trials of New Agents in Multiple Sclerosis appointed a Task Force that was charged with developing improved clinical outcome measures. This Task Force acquired contemporary clinical trial and historical multiple sclerosis data for meta-analyses of primary and secondary outcome assessments to provide a basis for recommending a new outcome measure. A composite measure encompassing the major clinical dimensions of arm, leg and cognitive function was identified and termed the multiple sclerosis functional composite (MSFC). The MSFC consists of three objective quantitative tests of neurological function which are easy to administer. Change in this MSFC over the first year of observation predicted subsequent change in the EDSS, suggesting that the MSFC is more sensitive to change than the EDSS. This paper provides details concerning the development and testing of the MSFC.