An LIR motif in the Rift Valley fever virus NSs protein is critical for the interaction with LC3 family members and inhibition of autophagy.

Rift Valley fever virus (RVFV) is a viral zoonosis that causes severe disease in ruminants and humans. The nonstructural small (NSs) protein is the primary virulence factor of RVFV that suppresses the host's antiviral innate immune response. Bioinformatic analysis and AlphaFold structural modeling identified four putative LC3-interacting regions (LIR) motifs (NSs 1-4) in the RVFV NSs protein, which suggest that NSs interacts with the host LC3-family proteins. Using, isothermal titration calorimetry, X-ray crystallography, co-immunoprecipitation, and co-localization experiments, the C-terminal LIR motif (NSs4) was confirmed to interact with all six human LC3 proteins. Phenylalanine at position 261 (F261) within NSs4 was found to be critical for the interaction of NSs with LC3, retention of LC3 in the nucleus, as well as the inhibition of autophagy in RVFV infected cells. These results provide mechanistic insights into the ability of RVFV to overcome antiviral autophagy through the interaction of NSs with LC3 proteins.

Structural and functional characterization of the role of acetylation on the interactions of the human Atg8-family proteins with the autophagy receptor TP53INP2/DOR.

The Atg8-family proteins (MAP1LC3/LC3A, LC3B, LC3C, GABARAP, GABARAPL1 and GABARAPL2) play a pivotal role in macroautophagy/autophagy through their ability to help form autophagosomes. Although autophagosomes form in the cytoplasm, nuclear levels of the Atg8-family proteins are significant. Recently, the nuclear/cytoplasmic shuttling of LC3B was shown to require deacetylation of two Lys residues (K49 and K51 in LC3B), which are conserved in Atg8-family proteins. To exit the nucleus, deacetylated LC3B must bind TP53INP2/DOR (tumor protein p53 inducible nuclear protein 2) through interaction with the LC3-interacting region (LIR) of TP53INP2 (TP53INP2LIR). To examine their selectivity for TP53INP2 and the role of the conserved Lys residues in Atg8-family proteins, we prepared the six human Atg8-family proteins and acetylated variants of LC3A and GABARAP for biophysical and structural characterization of their interactions with the TP53INP2LIR. Isothermal titration calorimetry (ITC) experiments demonstrate that this LIR binds preferentially to GABARAP subfamily proteins, and that only acetylation of the second Lys residue reduces binding to GABARAP and LC3A. Crystal structures of complexes with GABARAP and LC3A (acetylated and deacetylated) define a ß-sheet in the TP53INP2LIR that determines the GABARAP selectivity and establishes the importance of acetylation at the second Lys. The in vitro results were confirmed in cells using acetyl-mimetic variants of GABARAP and LC3A to examine nuclear/cytoplasmic shuttling and colocalization with TP53INP2. Together, the results demonstrate that TP53INP2 shows selectivity to the GABARAP subfamily and acetylation at the second Lys of GABARAP and LC3A disrupts key interactions with TP53INP2 required for their nuclear/cytoplasmic shuttling.

MicroRNAs as biomarkers in spontaneous intracerebral hemorrhage: A systematic review of recent clinical evidence.

OBJECTIVES: Spontaneous intracerebral hemorrhage (SICH) is a subtype of stroke associated with high mortality and devastating disabilities. Therefore, identifying non-invasive biomarkers for SICH would have a tremendous clinical impact. MicroRNAs (miRNAs) are non-coding single-stranded RNAs containing 21-23 nucleotides that control the activity of various protein-coding genes through post-transcriptional repression. In this systematic review, we report the recent clinical evidence on the role of miRNAs as biomarkers for the prediction, prognosis, early detection, and risk stratification of SICH. METHODS: We conducted a systematic search of PubMed, PubMed Central, MEDLINE, and Embase databases and included only full-text peer-reviewed articles published in English. RESULTS: We included 10 studies comprising seven case-control studies, two cohort studies, and one cross-sectional study, among which we found 27 altered miRNAs, suggesting their role as biomarkers for the early detection of ICH. Additionally, the expression of 34 miRNAs was associated with poor prognosis of ICH; miR-126 and miR-23a-3p expression correlated with relative perihematomal edema (PHE) volume, and using a subset of 10 miRNA signatures had an accuracy of 100% in predicting hematoma in patients with ICH. Moreover, miR-4317 and miR-4325 profiling predicted the development of late seizures. Thirty-nine miRNAs were associated with the incidence of all types of strokes, while 10 miRNAs correlated with the predicted risk of stroke but were not specific to a stroke subtype. The altered miRNA signatures contributed to endothelial dysfunction, hematoma, and PHE through leukocyte activation, oxidative stress response, programmed cell death, smooth muscle cell proliferation, and apoptosis of cerebrovascular endothelial cells. The current data had limitations and gaps, especially the human studies, and there may have been selection bias in the prospective studies. There were also some limitations regarding the methods for obtaining miRNAs and identifying target RNAs specific to SICH pathology. Additionally, there may have been correlations between the outcomes and other factors, such as therapeutic interventions and ICH severity, the circulating miRNA profiles and gene expression profiles, and other pathological conditions and patients' age. Finally, the prediction and risk stratification of SICH could not be calculated separately from ischemic stroke. CONCLUSIONS: Following our literature retrieval, we noted alterations in various miRNA signatures, suggesting their potential role as biomarkers for the early detection and differentiation of SICH. Indeed, miRNA expression was associated with a poor prognosis of SICH and correlated with the predicted risk of stroke but was not specific to a stroke subtype. Further studies are needed, especially on the therapeutic potential of miRNAs and their target RNAs in SICH.