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37 p.-3 fig.-1 tab., Mitochondria are dynamic, multifunctional cellular organelles that play a fundamental role in maintaining cellular homeostasis. Keeping the quality of mitochondria in check is of essential importance for functioning and survival of the cells. Selective autophagic clearance of flawed mitochondria, a process termed mitophagy, is one of the most prominent mechanisms through which cells maintain a healthy mitochondrial pool. The best-studied pathway through which mitophagy is exerted is the PINK1-PRKN pathway. However, an increasing number of studies have shown an existence of alternative pathways, where different proteins and lipids are able to recruit autophagic machinery independently of PINK1 and PRKN. The significance of PRKN-independent mitophagy pathways is reflected in various physiological and pathophysiological processes, but many questions regarding the regulation and the interplay between these pathways remain open. Here we review the current knowledge and recent progress made in the field of PRKN-independent mitophagy. Particularly we focus on the regulation of various receptors that participate in targeting impaired mitochondria to autophagosomes independently of PRKN., We are grateful for funding from the Israel Science Foundation (Grant #215/19), the Sagol Longevity Foundation, Joint NRF - ISF Research Fund (Grant #3221/19), and the Yeda-Sela Center for Basic Research, as well as the Research Council of Norway through its Centres of Excellence funding scheme (project number 262652 to AS) and FRIPRO (project number 221831 to AS) and the Norwegian Cancer Society (project number 171318 to AS). Research in PB lab is supported by (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) PGC2018-098557-B-I00 Neuroscience Projects from Fundación Tatiana Pérez de Guzmán el Bueno and 2017/BMD-3813 from Comunidad de Madrid. The first authors are supported by a Marie Skłodowska-Curie ETN grant under the European Union’s Horizon 2020 Research and Innovation Programme (Grant Agreement No 765912 DRIVE)

During autophagy, cytosolic cargo is sequestered into double-membrane vesicles called autophagosomes. The origin and identity of the membranes that form the autophagosome remain to be fully characterized. Here, we investigated the role of cholesterol in starvation- induced autophagy and identify a role for the ER-localized cholesterol transport protein GRAMD1C in the regulation of autophagy and mitochondrial function. We demonstrate that cholesterol depletion leads to a rapid induction of autophagy, possibly caused by a corresponding increased abundance of curved autophagy membranes. We further show that GRAMD1C is a negative regulator of starvation-induced autophagy. Similar to its yeast orthologue, GRAMD1C is recruited to mitochondria through its GRAM domain. Additionally, we find that GRAMD1C depletion leads to increased mitochondrial cholesterol accumulation and mitochondrial oxidative phosphorylation. Finally, we demonstrate that expression of GRAM family genes is linked to clear cell renal carcinoma survival, highlighting the pathophysiological relevance of cholesterol transport proteins.

During autophagy, cytosolic cargo is sequestered into double-membrane vesicles called autophagosomes. The contributions of specific lipids, such as cholesterol, to the membranes that form the autophagosome, remain to be fully characterized. Here, we demonstrate that short term cholesterol depletion leads to a rapid induction of autophagy and a corresponding increase in autophagy initiation events. We further show that the ER-localized cholesterol transport protein GRAMD1C functions as a negative regulator of starvation-induced autophagy and that both its cholesterol transport VASt domain and membrane binding GRAM domain are required for GRAMD1C-mediated suppression of autophagy initiation. Similar to its yeast orthologue, GRAMD1C associates with mitochondria through its GRAM domain. Cells lacking GRAMD1C or its VASt domain show increased mitochondrial cholesterol levels and mitochondrial oxidative phosphorylation, suggesting that GRAMD1C may facilitate cholesterol transfer at ER-mitochondria contact sites. Finally, we demonstrate that expression of GRAMD family proteins is linked to clear cell renal carcinoma survival, highlighting the pathophysiological relevance of cholesterol transport proteins.

Knockout collections are invaluable tools for studying model organisms such as yeast. However, there are no large-scale knockout collections of human cells. Using gene-trap mutagenesis in near-haploid human cells, we established a platform to generate and isolate individual 'gene-trapped cells' and used it to prepare a collection of human cell lines carrying single gene-trap insertions. In most cases, the insertion can be reversed. This growing library covers 3,396 genes, one-third of the expressed genome, is DNA-barcoded and allows systematic screens for a wide variety of cellular phenotypes. We examined cellular responses to TNF-α, TGF-β, IFN-γ and TNF-related apoptosis-inducing ligand (TRAIL), to illustrate the value of this unique collection of isogenic human cell lines.

Background Chromosomal translocations are a hallmark of cancer cells and give rise to fusion oncogenes. To gain insight into the mechanisms governing tumorigenesis, adequate model cell lines are required. Results We employ the versatile CRISPR/Cas system to engineer cell lines in which chromosomal translocations are either generated de novo (CD74-ROS1) or existing translocations are reverted back to the original configuration (BCR-ABL1). To this end, we co-apply two guide RNAs to artificially generate two breakpoints and screen for spontaneous fusion events by PCR. Conclusions The approach we use is efficient and delivers clones bearing translocationsin a predictable fashion. Detailed analysis suggests that the clones display no additional undesired alterations, implying that the approach is robust and precise. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3084-5) contains supplementary material, which is available to authorized users.