ULP-2 SUMO Protease Regulates E-Cadherin Recruitment to Adherens Junctions

ULP-2 SUMO protease regulates UPRmt and mitochondrial homeostasis in Caenorhabditis elegans

Mitochondria are the powerhouses of cells, responsible for energy production and regulation of cellular homeostasis. When mitochondrial function is impaired, a stress response termed mitochondrial unfolded protein response (UPRmt) is initiated to restore mitochondrial function. Since mitochondria and UPRmt are implicated in many diseases, it is important to understand UPRmt regulation. In this study, we show that the SUMO protease ULP-2 has a key role in regulating mitochondrial function and UPRmt. Specifically, down-regulation of ulp-2 suppresses UPRmt and reduces mitochondrial membrane potential without significantly affecting cellular ROS. Mitochondrial networks are expanded in ulp-2 null mutants with larger mitochondrial area and increased branching. Moreover, the amount of mitochondrial DNA is increased in ulp-2 mutants. Downregulation of ULP-2 also leads to alterations in expression levels of mitochondrial genes involved in protein import and mtDNA replication, however, mitophagy remains unaltered. In summary, this study demonstrates that ULP-2 is required for mitochondrial homeostasis and the UPRmt.

Protective effect of vitamin C against ivermectin induced nephrotoxicity in different age groups of male wistar rats: bio-histopathological study

Ivermectin (Ive) has exceedingly efficient against several microorganisms including viruses; therefore, it could help as a potential treatment of COVID-19. Because of increasing consumption of ivermectin and vitamin C (Vit.C) in hope to treat COVID-19, and because of ivermectin nephrotoxic effects have not been fully clarified especially in juvenile age, it was conducted to examine the histopathological and biochemical effects of ivermectin on adult and juvenile kidneys, and to assess the possible protective role of Vit.C against this potential toxicity. Rats were divided to 4 subgroups (Control subgroup, Vit.C subgroup, Ive subgroup, and Vit.C+Ive subgroup), 1 week after 4 doses of ivermectin (0.4 mg/kg Ive±1.25 mg/kg Vit.C), blood samples obtained for assessment of kidney function test, part of kidneys prepared for determination of matrix metalloproteinase-9 and antioxidant enzymes essay. Other parts prepared for histopathological and ultrastructural examination. Results showed that administration of ivermectin led to attenuation in kidney function and in activities of the antioxidant enzymes and increase in matrix metalloproteinase-9 activity. In addition, there were histological damages (shrunken glomeruli, widened urinary space, cytoplasmic vacuolation and pyknotic nuclei with epithelial exfoliation, extravasated blood, and mononuclear cell infiltration) and immunohistochemistry revealed increase in percentage of Bax proapoptotic protein expression. Also, ultrastructure examination showed alteration in cell architecture. All these changes were more obvious in juvenile group while co-administration of Vit.C led to significant protection more in adult group. In conclusion, Ivermectin should be used cautiously especially in juvenile age, and co-administration of Vit.C is highly recommended.

The role of SUMOylation during development

During the development of multicellular organisms, transcriptional regulation plays an important role in the control of cell growth, differentiation and morphogenesis. SUMOylation is a reversible post-translational process involved in transcriptional regulation through the modification of transcription factors and through chromatin remodelling (either modifying chromatin remodelers or acting as a ‘molecular glue’ by promoting recruitment of chromatin regulators). SUMO modification results in changes in the activity, stability, interactions or localization of its substrates, which affects cellular processes such as cell cycle progression, DNA maintenance and repair or nucleocytoplasmic transport. This review focuses on the role of SUMO machinery and the modification of target proteins during embryonic development and organogenesis of animals, from invertebrates to mammals.

SUMO modification in apoptosis

Apoptosis and clearance of dead cells is highly evolutionarily conserved from nematode to humans, which is crucial to the growth and development of multicellular organism. Fail to remove apoptotic cells often lead to homeostasis imbalance, fatal autoimmune diseases, and neurodegenerative diseases. Small ubiquitin-related modifiers (SUMOs) modification is a post-translational modification of ubiquitin proteins mediated by the sentrin-specific proteases (SENPs) family. SUMO modification is widely involved in many cellular biological process, and abnormal SUMO modification is also closely related to many major human diseases. Recent researches have revealed that SUMO modification event occurs during apoptosis and clearance of apoptotic cells, and plays an important role in the regulation of apoptotic signaling pathways. This review summarizes some recent progress in the revelation of regulatory mechanisms of these pathways and provides some potential researching hotpots of the SUMO modification regulation to apoptosis.

Game of Tissues: How the Epidermis Thrones C. elegans Shape

The versatility of epithelial cell structure is universally exploited by organisms in multiple contexts. Epithelial cells can establish diverse polarized axes within their tridimensional structure which enables them to flexibly communicate with their neighbors in a 360° range. Hence, these cells are central to multicellularity, and participate in diverse biological processes such as organismal development, growth or immune response and their misfunction ultimately impacts disease. During the development of an organism, the first task epidermal cells must complete is the formation of a continuous sheet, which initiates its own morphogenic process. In this review, we will focus on the C. elegans embryonic epithelial morphogenesis. We will describe how its formation, maturation, and spatial arrangements set the final shape of the nematode C. elegans. Special importance will be given to the tissue-tissue interactions, regulatory tissue-tissue feedback mechanisms and the players orchestrating the process.

SUMO peptidase ULP-4 regulates mitochondrial UPR-mediated innate immunity and lifespan extension

Animals respond to mitochondrial stress with the induction of mitochondrial unfolded protein response (UPR^mt). A cascade of events occur upon UPR^mt activation, ultimately triggering a transcriptional response governed by two transcription factors: DVE-1 and ATFS-1. Here we identify SUMO-specific peptidase ULP-4 as a positive regulator of C. elegans UPR^mt to control SUMOylation status of DVE-1 and ATFS-1. SUMOylation affects these two axes in the transcriptional program of UPR^mt with distinct mechanisms: change of DVE-1 subcellular localization vs. change of ATFS-1 stability and activity. Our findings reveal a post-translational modification that promotes immune response and lifespan extension during mitochondrial stress.

Most animal cells carry compartments called mitochondria. These tiny powerhouses produce the energy that fuels many life processes, but they also store important compounds and can even cause an infected or defective cell to kill itself. For a cell, keeping its mitochondria healthy is often a matter of life and death: failure to do so is linked with aging, cancer or diseases such as Alzheimer’s.

The cell uses a surveillance program called the mitochondrial unfolded protein response to assess the health of its mitochondria. If something is amiss, the cell activates specific mechanisms to fix the problem, which involves turning on specific genes in its genome.

A protein named ULP-4, which is found in the worm Caenorhabditis elegans but also in humans, participates in this process. This enzyme cuts off chemical ‘tags’ known as SUMO from proteins. Adding and removing these labels changes the place and role of a protein in the cell. However, it was still unclear how ULP-4 played a role in the mitochondrial unfolded protein response.

Here, Gao et al. show that when mitochondria are in distress, ULP-4 removes SUMO from DVE-1 and ATFS-1, two proteins that control separate arms of the mitochondrial unfolded protein response. Without SUMO tags, DVE-1 can relocate to the area in the cell where it can turn on genes that protect and repair mitochondria; meanwhile SUMO-free ATFS-1 becomes more stable and can start acting on the genome. Finally, the experiments show that removing SUMO on DVE-1 and ATFS-1 is essential to keep the worms healthy and with a long lifespan under mitochondrial stress.

The experiments by Gao et al. show that the mitochondrial unfolded protein response relies, at least in part, on SUMO tags. This knowledge opens new avenues of research, and could help fight diseases that emerge when mitochondria fail.

Mitotic and Meiotic Functions for the SUMOylation Pathway in the Caenorhabditis elegans Germline

Meiosis is a highly regulated process, partly due to the need to break and then repair DNA as part of the meiotic program. Post-translational modifications are widely used during meiotic events to regulate steps such as protein complex formation, checkpoint activation, and protein attenuation. In this paper, we investigate how proteins that are obligatory components of the SUMO (small ubiquitin-like modifier) pathway, one such post-translational modification, affect the Caenorhabditis elegans germline. We show that UBC-9, the E2 conjugation enzyme, and the C. elegans homolog of SUMO, SMO-1, localize to germline nuclei throughout prophase I. Mutant analysis of smo-1 and ubc-9 revealed increased recombination intermediates throughout the germline, originating during the mitotic divisions. SUMOylation mutants also showed late meiotic defects including defects in the restructuring of oocyte bivalents and endomitotic oocytes. Increased rates of noninterfering crossovers were observed in ubc-9 heterozygotes, even though interfering crossovers were unaffected. We have also identified a physical interaction between UBC-9 and DNA repair protein MRE-11 ubc-9 and mre-11 null mutants exhibited similar phenotypes at germline mitotic nuclei and were synthetically sick. These phenotypes and genetic interactions were specific to MRE-11 null mutants as opposed to RAD-50 or resection-defective MRE-11 We propose that the SUMOylation pathway acts redundantly with MRE-11, and in this process MRE-11 likely plays a structural role.

Comprehensive list of SUMO targets in Caenorhabditis elegans and its implication for evolutionary conservation of SUMO signaling

Post-translational modification by small ubiquitin-related modifier (SUMO) is a key regulator of cell physiology, modulating protein-protein and protein-DNA interactions. Recently, SUMO modifications were postulated to be involved in response to various stress stimuli. We aimed to identify the near complete set of proteins modified by SUMO and the dynamics of the modification in stress conditions in the higher eukaryote, Caenorhabditis elegans. We identified 874 proteins modified by SUMO in the worm. We have analyzed the SUMO modification in stress conditions including heat shock, DNA damage, arsenite induced cellular stress, ER and osmotic stress. In all these conditions the global levels of SUMOylation was significantly increased. These results show the evolutionary conservation of SUMO modifications in reaction to stress. Our analysis showed that SUMO targets are highly conserved throughout species. By comparing the SUMO targets among species, we approximated the total number of proteins modified in a given proteome to be at least 15–20%. We developed a web server designed for convenient prediction of potential SUMO modification based on experimental evidences in other species.

Structural and functional analysis of SMO-1, the SUMO homolog in Caenorhabditis elegans

SUMO proteins are important post-translational modifiers involved in multiple cellular pathways in eukaryotes, especially during the different developmental stages in multicellular organisms. The nematode C. elegans is a well known model system for studying metazoan development and has a single SUMO homolog, SMO-1. Interestingly, SMO-1 modification is linked to embryogenesis and development in the nematode. However, high-resolution information about SMO-1 and the mechanism of its conjugation is lacking. In this work, we report the high-resolution three dimensional structure of SMO-1 solved by NMR spectroscopy. SMO-1 has flexible N-terminal and C-terminal tails on either side of a rigid beta-grasp folded core. While the sequence of SMO-1 is more similar to SUMO1, the electrostatic surface features of SMO-1 resemble more with SUMO2/3. SMO-1 can bind to typical SUMO Interacting Motifs (SIMs). SMO-1 can also conjugate to a typical SUMOylation consensus site as well as to its natural substrate HMR-1. Poly-SMO-1 chains were observed in-vitro even though SMO-1 lacks any consensus SUMOylation site. Typical deSUMOylation enzymes like Senp2 can cleave the poly-SMO-1 chains. Despite being a single gene, the SMO-1 structure allows it to function in a large repertoire of signaling pathways involving SUMO in C. elegans. Structural and functional features of SMO-1 studies described here will be useful to understand its role in development.

Reversion of epithelial-mesenchymal transition by a novel agent DZ-50 via IGF binding protein-3 in prostate cancer cells

Dysregulation of transforming growth factor-β1 (TGF-β1) and insulin-like growth factor (IGF) axis has been linked to reactive stroma dynamics in prostate cancer progression. IGF binding protein-3 (IGFBP3) induction is initiated by stroma remodeling and could represent a potential therapeutic target for prostate cancer. In previous studies a lead quinazoline-based Doxazosin® derivative, DZ-50, impaired prostate tumor growth by targeting proteins involved in focal adhesion, anoikis resistance and epithelial-mesenchymal-transition (EMT). This study demonstrates that DZ-50 increased expression of the epithelial marker E-cadherin, and decreased the mesenchymal marker N-cadherin in human prostate cancer cells. In DU-145 cells, the effect of DZ-50 on EMT towards mesenchymal epithelial transition (MET) was inhibited by talin1 overexpression, a focal adhesion regulator promoting anoikis resistance and tumor invasion. DZ-50 treatment of human prostate cancer cells and cancer-associated fibroblasts (CAFs) downregulated IGFBP3 expression at mRNA and protein level. In TGF-β1 responsive LNCaPTβRII, TGF-β1 reversed DZ-50-induced MET by antagonizing the drug-induced decrease of nuclear IGFBP3. Furthermore, co-culture with CAFs promoted prostate cancer epithelial cell invasion, an effect that was significantly inhibited by DZ-50. Our findings demonstrate that the lead compound, DZ-50, inhibited the invasive properties of prostate cancer epithelial cells by targeting IGFBP3 and mediating EMT conversion to MET. This study integrated the mechanisms underlying the effect of DZ-50 and further supported the therapeutic value of this compound in the treatment of advanced metastatic prostate cancer.

Adherens Junctions on the Move-Membrane Trafficking of E-Cadherin

Cadherin-based adherens junctions are conserved structures that mediate epithelial cell-cell adhesion in invertebrates and vertebrates. Despite their pivotal function in epithelial integrity, adherens junctions show a remarkable plasticity that is a prerequisite for tissue architecture and morphogenesis. Epithelial cadherin (E-cadherin) is continuously turned over and undergoes cycles of endocytosis, sorting and recycling back to the plasma membrane. Mammalian cell culture and genetically tractable model systems such as Drosophila have revealed conserved, but also distinct, mechanisms in the regulation of E-cadherin membrane trafficking. Here, we discuss our current knowledge about molecules and mechanisms controlling endocytosis, sorting and recycling of E-cadherin during junctional remodeling.

A SUMO-Dependent Protein Network Regulates Chromosome Congression during Oocyte Meiosis

During Caenorhabditis elegans oocyte meiosis, a multi-protein ring complex (RC) localized between homologous chromosomes, promotes chromosome congression through the action of the chromokinesin KLP-19. While some RC components are known, the mechanism of RC assembly has remained obscure. We show that SUMO E3 ligase GEI-17/PIAS is required for KLP-19 recruitment to the RC, and proteomic analysis identified KLP-19 as a SUMO substrate in vivo. In vitro analysis revealed that KLP-19 is efficiently sumoylated in a GEI-17-dependent manner, while GEI-17 undergoes extensive auto-sumoylation. GEI-17 and another RC component, the kinase BUB-1, contain functional SUMO interaction motifs (SIMs), allowing them to recruit SUMO modified proteins, including KLP-19, into the RC. Thus, dynamic SUMO modification and the presence of SIMs in RC components generate a SUMO-SIM network that facilitates assembly of the RC. Our results highlight the importance of SUMO-SIM networks in regulating the assembly of dynamic protein complexes.

Another morphogenetic movement on the map: Charting dorsal intercalation in C. elegans

Dorsal intercalation is a coordinated cell migration event that rearranges hypodermal cells during C. elegans embryogenesis, and that resembles cell intercalation in many systems from flies to mice. Despite its conservation, the molecular mechanisms that govern dorsal intercalation in worms have remained elusive. Here, we comment on our recent publication, Walck-Shannon et al.,(1) which begins to spatially map the molecular requirements for intercalation. First, we provide a historical perspective on the factors that have previously hampered the study of dorsal intercalation. Next, we provide a summary of the molecular pathways identified in Walck-Shannon et al.,(1) pointing out surprises along the way. Finally, we consider the potential conservation of the molecular pathway we described and discuss future questions surrounding dorsal intercalation. Despite the challenges, dorsal intercalation is a process poised to advance our understanding of cell intercalation during morphogenesis throughout the animal kingdom.

Adhesion with a Sumo

Adherens junctions (AJs) play a crucial role in epithelial tissue development and tumorigenesis, and the mechanisms controlling their assembly and disassembly have therefore attracted considerable attention. A paper from Tsur et al. (2015) in this issue of Developmental Cell now shows how sumoylation and desumoylation of E-cadherin promotes its recruitment to AJs.

Tools to Study SUMO Conjugation in Caenorhabditis elegans

The cell biology of sumoylation has mostly been studied using transformed cultured cells and yeast. In recent years, genetic analysis has demonstrated important roles for sumoylation in the biology of C. elegans. Here, we expand the existing set of tools making it possible to address the role of sumoylation in the nematode C. elegans using a combination of genetics, imaging, and biochemistry. Most importantly, the dynamics of SUMO conjugation and deconjugation can be followed very precisely both in space and time within living worms. Additionally, the biochemistry of SUMO conjugation and deconjugation can be addressed using recombinant purified components of the C. elegans sumoylation machinery, including E3 ligases and SUMO proteases. These tools and reagents will be useful to gain insights into the biological role of SUMO in the context of a multicellular organism.