Exploring the eukaryotic Yip and REEP/Yop superfamily of membrane-shaping adapter proteins (MSAPs): A cacophony or harmony of structure and function?

ADP ribosylation factor-like GTPase 6-interacting protein 5 (Arl6IP5) is an ER membrane-shaping protein that modulates ER-phagy

The endoplasmic reticulum (ER) is the membrane-bound organelle characterized by the reticular network of tubules. It is well established that the ER tubules are shaped by ER membrane proteins containing the conserved reticulon-homology domain (RHD). Membrane shaping by the RHD-containing proteins is also involved in the regulation of ER-phagy, selective autophagy of the ER. However, it remains unclear whether there exists ER membrane-shaping proteins other than the RHD-containing proteins. In this study, we characterize Arl6IP5, an ER membrane protein containing the conserved PRA1 domain, as an ER membrane-shaping protein. Upon overexpression, Arl6IP5 induces the extensive network of the ER tubules and constricts the ER membrane as judged by exclusion of a luminal ER enzyme from the ER tubules. The membrane constriction by Arl6IP5 allows the cells to maintain the tubular ER network in the absence of microtubules. siRNA-mediated knockdown of Arl6IP5 impairs the ER morphology, and the phenotype of the Arl6IP5 knockdown cells is rescued by exogenous expression of Arl6IP1, an RHD-containing protein. Furthermore, exogenous expression of Arl6IP5 rescues the phenotype of Arl6IP1 knockdown cells, and the PRA1 domain is sufficient to rescue it. Upon disruption of the possible short hairpin structures of the PRA1 domain, Arl6IP5 abolishes membrane constriction. The siRNA-mediated knockdown of Arl6IP5 impairs flux of the ER-phagy mediated by FAM134B. These results indicate that Arl6IP5 acts as an ER membrane-shaping protein involved in the regulation of ER-phagy, implying that the PRA1 domain may serve as a general membrane-shaping unit other than the RHD.

YIPF2 regulates genome integrity

Understanding of the mechanisms for genome integrity maintenance can help in developing effective intervention strategies to combat aging. A whole-genome RNAi screen was conducted to identify novel factors involved in maintaining genome stability. The potential target genes identified in the screening are related to the cell cycle, proteasome, and spliceosomes. Unexpectedly, the Golgi protein YIPF2 has been found to play a critical role in maintaining genome stability. The depletion of YIPF2 hinders the process of homologous recombination (HR) repair, which then triggers DNA damage response mechanisms, ultimately leading to cellular senescence. The overexpression of YIPF2 facilitated cellular recovery from DNA damage induced by chemotherapy agents or replicative senescence-associated DNA damage. Our findings indicate that only the intact Golgi apparatus containing YIPF2 provides a protective effect on genome integrity.

Molecular Responses of Anti-VEGF Therapy in Neovascular Age-Related Macular Degeneration: Integrative Insights From Multi-Omics and Clinical Imaging

Purpose

The purpose of this study was to investigate the molecular mechanisms underlying anti-vascular endothelial growth factor (anti-VEGF) efficacy and response variability in neovascular age-related macular degeneration (nAMD) using longitudinal proteomic and metabolomic analysis alongside three-dimensional lesion measurements.

Methods

In this prospective study, 54 treatment-naive patients with nAMD underwent "3+ pro re nata" (3+PRN) anti-VEGF regimens followed for at least 12 weeks. Aqueous humors were collected pre- and post-treatment for proteomic and metabolomic analysis. Three-dimensional optical coherence tomography (OCT) and OCT angiography assessed different types of nAMD lesion volumes and areas.

Results

There were 1350 proteins and 1268 metabolites that were identified in aqueous humors, with 301 proteins and 353 metabolites significantly altered during anti-VEGF treatment, enriched in pathways of angiogenesis, energy metabolism, signal transduction, and neurofunctional regulation. Sixty-seven changes of (Δ) molecules significantly correlated with at least one type of ΔnAMD lesion. Notably, proteins FGA, TALDO1, and ASPH significantly decreased during treatment, with their reductions correlating with greater lesion regression in at least two lesion types. Conversely, despite that YIPF3 also showed significant downregulation, its decrease was associated with poorer regression in total nAMD lesion and subretinal hyper-reflective material.

Conclusions

This study identifies FGA, TALDO1, and ASPH as potential key molecules in the efficacy of anti-VEGF therapy, whereas YIPF3 may be a key factor in poor response. The integration of longitudinal three-dimensional lesion analysis with multi-omics provides valuable insights into the mechanisms and response variability of anti-VEGF treatment in nAMD.

AtHVA22a, a plant-specific homologue of Reep/DP1/Yop1 family proteins is involved in turnip mosaic virus propagation

The movement of potyviruses, the largest genus of single-stranded, positive-sense RNA viruses responsible for serious diseases in crops, is very complex. As potyviruses developed strategies to hijack the host secretory pathway and plasmodesmata (PD) for their transport, the goal of this study was to identify membrane and/or PD-proteins that interact with the 6K2 protein, a potyviral protein involved in replication and cell-to-cell movement of turnip mosaic virus (TuMV). Using split-ubiquitin membrane yeast two-hybrid assays, we screened an Arabidopsis cDNA library for interactors of TuMV6K2. We isolated AtHVA22a (Hordeum vulgare abscisic acid responsive gene 22), which belongs to a multigenic family of transmembrane proteins, homologous to Receptor expression-enhancing protein (Reep)/Deleted in polyposis (DP1)/Yop1 family proteins in animal and yeast. HVA22/DP1/Yop1 family genes are widely distributed in eukaryotes, but the role of HVA22 proteins in plants is still not well known, although proteomics analysis of PD fractions purified from Arabidopsis suspension cells showed that AtHVA22a is highly enriched in a PD proteome. We confirmed the interaction between TuMV6K2 and AtHVA22a in yeast, as well as in planta by using bimolecular fluorescence complementation and showed that TuMV6K2/AtHVA22a interaction occurs at the level of the viral replication compartment during TuMV infection. Finally, we showed that the propagation of TuMV is increased when AtHVA22a is overexpressed in planta but slowed down upon mutagenesis of AtHVA22a by CRISPR-Cas9. Altogether, our results indicate that AtHVA22a plays an agonistic effect on TuMV propagation and that the C-terminal tail of the protein is important in this process.