ARL8B mediates lipid droplet contact and delivery to lysosomes for lipid remobilization.

Lipid droplets (LDs) play a crucial role in maintaining cellular lipid balance by storing and delivering lipids as needed. However, the intricate lipolytic pathways involved in LD turnover remain poorly described, hindering our comprehension of lipid catabolism and related disorders. Here, we show a function of the small GTPase ARL8B in mediating LD turnover in lysosomes. ARL8B-GDP localizes to LDs, while ARL8-GTP predominantly favors lysosomes. GDP binding induces a conformation with an exposed N-terminal amphipathic helix, enabling ARL8B to bind to LDs. By associating with LDs and lysosomes, and with its property to form a heterotypic complex, ARL8B mediates LD-lysosome contacts and efficient lipid transfer between these organelles. In human macrophages, this ARL8B-dependent LD turnover mechanism appears as the major lipolytic pathway. Our finding opens exciting possibilities for understanding the molecular mechanisms underlying LD degradation and its potential implications for inflammatory disorders.

High throughput detection and genetic epidemiology of SARS-CoV-2 using COVIDSeq next-generation sequencing.

The rapid emergence of coronavirus disease 2019 (COVID-19) as a global pandemic affecting millions of individuals globally has necessitated sensitive and high-throughput approaches for the diagnosis, surveillance, and determining the genetic epidemiology of SARS-CoV-2. In the present study, we used the COVIDSeq protocol, which involves multiplex-PCR, barcoding, and sequencing of samples for high-throughput detection and deciphering the genetic epidemiology of SARS-CoV-2. We used the approach on 752 clinical samples in duplicates, amounting to a total of 1536 samples which could be sequenced on a single S4 sequencing flow cell on NovaSeq 6000. Our analysis suggests a high concordance between technical duplicates and a high concordance of detection of SARS-CoV-2 between the COVIDSeq as well as RT-PCR approaches. An in-depth analysis revealed a total of six samples in which COVIDSeq detected SARS-CoV-2 in high confidence which were negative in RT-PCR. Additionally, the assay could detect SARS-CoV-2 in 21 samples and 16 samples which were classified inconclusive and pan-sarbeco positive respectively suggesting that COVIDSeq could be used as a confirmatory test. The sequencing approach also enabled insights into the evolution and genetic epidemiology of the SARS-CoV-2 samples. The samples were classified into a total of 3 clades. This study reports two lineages B.1.112 and B.1.99 for the first time in India. This study also revealed 1,143 unique single nucleotide variants and added a total of 73 novel variants identified for the first time. To the best of our knowledge, this is the first report of the COVIDSeq approach for detection and genetic epidemiology of SARS-CoV-2. Our analysis suggests that COVIDSeq could be a potential high sensitivity assay for the detection of SARS-CoV-2, with an additional advantage of enabling the genetic epidemiology of SARS-CoV-2.