The Role of Sumoylation in Senescence

Age-related p53 SUMOylation accelerates senescence and tau pathology in Alzheimer's disease

Aging is a major risk factor for Alzheimer's disease (AD). With the prevalence of AD increased, a mechanistic linkage between aging and the pathogenesis of AD needs to be further addressed. Here, we report that a small ubiquitin-related modifier (SUMO) modification of p53 is implicated in the process which remarkably increased in AD patient's brain. Mechanistically, SUMOylation of p53 at K386 residue causes the dissociation of SET/p53 complex, thus releasing SET into the cytoplasm, SET further interacts with cytoplasmic PP2A and inhibits its activity, resulting in tau hyperphosphorylation in neurons. In addition, SUMOylation of p53 promotes the p53 Ser15 phosphorylation that mediates neuronal senescence. Notably, p53 SUMOylation contributes to synaptic damage and cognitive defects in AD model mice. We also demonstrate that the SUMOylation inhibiter, Ginkgolic acid, recovering several senescent phenotypes drove by p53 SUMOylation in primary neurons. These findings suggest a previously undiscovered etiopathogenic relationship between aging and AD that is linked to p53 SUMOylation and the potential of SUMOylated p53-based therapeutics for neurodegeneration such as Alzheimer's disease.

The intricate relationship between SUMOylation and gliomas: a review with a perspective on natural compounds

Gliomas are tumours that affect the nervous system, with glioblastoma, also known as grade IV astrocytoma, being the most aggressive type, associated with poor prognosis. Glioblastoma is characterised by its highly invasive nature, rapid growth, and resistance to conventional chemotherapy and radiation treatments, resulting in a median survival of about 14 months. To improve patient outcomes, novel therapeutic approaches are needed. Targeting SUMOylation, a post-translational modification involving the attachment of Small Ubiquitin-like Modifier (SUMO) proteins to lysine residues in target proteins, is emerging as a promising strategy. SUMOylation regulates various biological processes, including the cell cycle, apoptosis, and senescence. Dysregulation of this pathway has been linked to glioblastoma tumorigenesis, as well as the invasion and proliferation of glioblastoma cells. Therefore, focusing on the SUMOylation pathway offers the potential for developing innovative therapeutic strategies, including the use of natural compounds as adjuvant therapies, to address glioblastoma more effectively.

PTMD 2.0: an updated database of disease-associated post-translational modifications

Various post-translational modifications (PTMs) participate in nearly all aspects of biological processes by regulating protein functions, and aberrant states of PTMs are frequently associated with human diseases. Here, we present a comprehensive database of PTMs associated with diseases (PTMD 2.0), including 342 624 PTM-disease associations (PDAs) in 15 105 proteins for 93 types of PTMs and 2083 diseases. Based on the distinct PTM states in diseases, we classified all PDAs into six categories: upregulation (U) or downregulation (D) of PTM levels, absence (A) or presence (P) of PTMs, and creation (C) or disruption (N) of PTM sites. We provided detailed annotations for each PDA and carefully annotated disease-associated proteins by integrating the knowledge from 101 additional resources that covered 13 aspects, including disease-associated information, variation and mutation, protein-protein interaction, protein functional annotation, DNA and RNA element, protein structure, chemical-target relationship, mRNA expression, protein expression/proteomics, subcellular localization, biological pathway annotation, functional domain annotation and physicochemical property. With a data volume of ∼8 GB, we anticipate that PTMD 2.0 will serve as a fundamental resource for further analysing the relationships between PTMs and diseases. The online service of PTMD 2.0 is freely available at https://ptmd.biocuckoo.cn/.

Unravelling the molecular interplay: SUMOylation, PML nuclear bodies and vascular cell activity in health and disease

In the seemingly well-researched field of vascular research, there are still many underestimated factors and molecular mechanisms. In recent years, SUMOylation has become increasingly important. SUMOylation is a post-translational modification in which small ubiquitin-related modifiers (SUMO) are covalently attached to target proteins. Sites where these SUMO modification processes take place in the cell nucleus are PML nuclear bodies (PML-NBs) - multiprotein complexes with their essential main component and organizer, the PML protein. PML and SUMO, either alone or as partners, influence a variety of cellular processes, including regulation of transcription, senescence, DNA damage response and defence against microorganisms, and are involved in innate immunity and inflammatory responses. They also play an important role in maintaining homeostasis in the vascular system and in pathological processes leading to the development and progression of cardiovascular diseases. This review summarizes information about the function of SUMO(ylation) and PML(-NBs) in the human vasculature from angiogenesis to disease and highlights their clinical potential as drug targets.

Host SUMOylation Pathway Negatively Regulates Protective Immune Responses and Promotes Leishmania donovani Survival

SUMOylation is one of the post-translational modifications that have recently been described as a key regulator of various cellular, nuclear, metabolic, and immunological processes. The process of SUMOylation involves the modification of one or more lysine residues of target proteins by conjugation of a ubiquitin-like, small polypeptide known as SUMO for their degradation, stability, transcriptional regulation, cellular localization, and transport. Herein, for the first time, we report the involvement of the host SUMOylation pathway in the process of infection of Leishmania donovani, a causative agent of visceral leishmaniasis. Our data revealed that infection of L. donovani to the host macrophages leads to upregulation of SUMOylation pathway genes and downregulation of a deSUMOylating gene, SENP1. Further, to confirm the effect of the host SUMOylation on the growth of Leishmania, the genes associated with the SUMOylation pathway were silenced and parasite load was analyzed. The knockdown of the SUMOylation pathway led to a reduction in parasitic load, suggesting the role of the host SUMOylation pathway in the disease progression and parasite survival. Owing to the effect of the SUMOylation pathway in autophagy, we further investigated the status of host autophagy to gain mechanistic insights into how SUMOylation mediates the regulation of growth of L. donovani. Knockdown of genes of host SUMOylation pathway led to the reduction of the expression levels of host autophagy markers while promoting autophagosome–lysosome fusion, suggesting SUMOylation-mediated autophagy in terms of autophagy initiation and autophagy maturation during parasite survival. The levels of reactive oxygen species (ROS) generation, nitric oxide (NO) production, and pro-inflammatory cytokines were also elevated upon the knockdown of genes of the host SUMOylation pathway during L. donovani infection. This indicates the involvement of the SUMOylation pathway in the modulation of protective immune responses and thus favoring parasite survival. Taken together, the results of this study indicate the hijacking of the host SUMOylation pathway by L. donovani toward the suppression of host immune responses and facilitation of host autophagy to potentially facilitate its survival. Targeting of SUMOylation pathway can provide a starting point for the design and development of novel therapeutic interventions to combat leishmaniasis.

Protein of a thousand faces: The tumor-suppressive and oncogenic responses of p53

The p53 protein is a pleiotropic regulator working as a tumor suppressor and as an oncogene. Depending on the cellular insult and the mutational status, p53 may trigger opposing activities such as cell death or survival, senescence and cell cycle arrest or proliferative signals, antioxidant or prooxidant activation, glycolysis, or oxidative phosphorylation, among others. By augmenting or repressing specific target genes or directly interacting with cellular partners, p53 accomplishes a particular set of activities. The mechanism in which p53 is activated depends on increased stability through post-translational modifications (PTMs) and the formation of higher-order structures (HOS). The intricate cell death and metabolic p53 response are reviewed in light of gaining stability via PTM and HOS formation in health and disease.

Cutaneous and uveal melanoma: two different cancers in therapeutic needs

Melanocytes are located in various parts of the human body, such as the skin and the eye. Their transformation leads to melanoma, an aggressive and deadly neoplasm. Cutaneous and uveal melanomas show different characteristics, including significant differences in genetic alterations, metastatic sites and therapeutic response. In recent decades, great efforts have been made to obtain a more comprehensive understanding of genetics, genomics and molecular changes, enabling the identification of key cellular processes and signaling pathways in melanomas. Major breakthroughs were realized in the treatment of metastatic cutaneous melanoma, but most patients relapse. Currently, there is no approved systemic treatment for metastatic uveal melanoma. Thus, these two different cancers are in therapeutic need to overcome treatment failure and improve patient prognosis. In this review we discuss on one hand the mutation of MITF, the master gene of melanocyte homeostasis, which we identified as a new melanoma predisposition gene in cutaneous melanoma, and on the other hand the recent findings of intratumor heterogeneity and characterization of cell sub-populations in primary uveal melanomas. These studies offer new tools for early detection and therapeutic targets.

SUMOylation modification-mediated cell death

SUMOylation dynamically conjugates SUMO molecules to the lysine residue of a substrate protein, which depends on the physiological state of the cell and the attached SUMO isoforms. A prominent role of SUMOylation in molecular pathways is to govern the cellular death process. Herein, we summarize the association between SUMOylation modification events and four types of cellular death processes: apoptosis, autophagy, senescence and pyroptosis. SUMOylation positively or negatively regulates a certain cellular death pattern depending on specific conditions including the attached SUMO isoforms, disease types, substrate proteins and cell context. Moreover, we also discuss the possible role of SUMOylation in ferroptosis and propose a potential role of the SUMOylated GPX4 in the regulation of ferroptosis. Mapping the exact SUMOylation network with cellular death contributes to develop novel SUMOylation-targeting disease therapeutic strategies.

SUMOylation in α-Synuclein Homeostasis and Pathology

The accumulation and aggregation of α-synuclein are central to Parkinson’s disease (PD), yet the molecular mechanisms responsible for these events are not fully understood. Post-translational modifications of α-synuclein regulate several of its properties, including degradation, interaction with proteins and membranes, aggregation and toxicity. SUMOylation is a post-translational modification involved in various nuclear and extranuclear processes, such as subcellular protein targeting, mitochondrial fission and synaptic plasticity. Protein SUMOylation increases in response to several stressful situations, from viral infections to trauma. In this framework, an increasing amount of evidence has implicated SUMOylation in several neurodegenerative diseases, including PD. This review will discuss recent findings in the role of SUMOylation as a regulator of α-synuclein accumulation, aggregation and toxicity, and its possible implication in neurodegeneration that underlies PD.

Beyond Kinase Activity: ERK5 Nucleo-Cytoplasmic Shuttling as a Novel Target for Anticancer Therapy

The importance of mitogen-activated protein kinases (MAPK) in human pathology is underlined by the relevance of abnormalities of MAPK-related signaling pathways to a number of different diseases, including inflammatory disorders and cancer. One of the key events in MAPK signaling, especially with respect to pro-proliferative effects that are crucial for the onset and progression of cancer, is MAPK nuclear translocation and its role in the regulation of gene expression. The extracellular signal-regulated kinase 5 (ERK5) is the most recently discovered classical MAPK and it is emerging as a possible target for cancer treatment. The bigger size of ERK5 when compared to other MAPK enables multiple levels of regulation of its expression and activity. In particular, the phosphorylation of kinase domain and C-terminus, as well as post-translational modifications and chaperone binding, are involved in ERK5 regulation. Likewise, different mechanisms control ERK5 nucleo-cytoplasmic shuttling, underscoring the key role of ERK5 in the nuclear compartment. In this review, we will focus on the mechanisms involved in ERK5 trafficking between cytoplasm and nucleus, and discuss how these processes might be exploited to design new strategies for cancer treatment.

Modification of the base excision repair enzyme MBD4 by the small ubiquitin-like molecule SUMO1

The base excision repair DNA N-glycosylase MBD4 (also known as MED1), an interactor of the DNA mismatch repair protein MLH1, plays a central role in the maintenance of genomic stability of CpG sites by removing thymine and uracil from G:T and G:U mismatches, respectively. MBD4 is also involved in DNA damage response and transcriptional regulation. The interaction with other proteins is likely critical for understanding MBD4 functions. To identify novel proteins that interact with MBD4, we used tandem affinity purification (TAP) from HEK-293 cells. The MBD4-TAP fusion and its co-associated proteins were purified sequentially on IgG and calmodulin affinity columns; the final eluate was shown to contain MLH1 by western blotting, and MBD4-associated proteins were identified by mass spectrometry. Bands with molecular weight higher than that expected for MBD4 (˜66 kD) yielded peptides corresponding to MBD4 itself and the small ubiquitin-like molecule-1 (SUMO1), suggesting that MBD4 is sumoylated in vivo. MBD4 sumoylation was validated by co-immunoprecipitation in HEK-293 and MCF7 cells, and by an in vitrosumoylation assay. Sequence and mutation analysis identified three main sumoylation sites: MBD4 is sumoylated preferentially on K137, with additional sumoylation at K215 and K377. Patterns of MBD4 sumoylation were altered, in a DNA damage-specific way, by the anti-metabolite 5-fluorouracil, the alkylating agent N-Methyl-N-nitrosourea and the crosslinking agent cisplatin. MCF7 extract expressing sumoylated MBD4 displays higher thymine glycosylase activity than the unmodified species. Of the 67 MBD4 missense mutations reported in The Cancer Genome Atlas, 14 (20.9%) map near sumoylation sites. These results indicate that MBD4 is sumoylated in vivo in a DNA damage-specific manner, and suggest that sumoylation serves to regulate its repair activity and could be compromised in cancer. This study expands the role played by sumoylation in fine-tuning DNA damage response and repair.

SUMOylation in Neurodegenerative Diseases

Posttranslational modifications are ubiquitous regulators of cellular processes. The regulatory role of SUMOylation, the attachment of a small ubiquitin-related modifier to a target protein, has been implicated in fundamental processes like cell division, DNA damage repair, mitochondrial homeostasis, and stress responses. Recently, it is gaining more attention in drug discovery as well. As life expectancy keeps rising, more individuals are at risk for developing age-associated diseases. This not only makes a person's life uncomfortable, but it also places an economic burden on society. Therefore, finding treatments for age-related diseases is an important issue. Understanding the basic mechanisms in the cell under normal and disease conditions is fundamental for drug discovery. There is an increasing number of reports showing that the ageing process could be influenced by SUMOylation. Similarly, SUMOylation is essential for proper neuronal function. In this review we summarize the latest results regarding the connection between SUMOylation and neurodegenerative diseases. We highlight the significance of specific SUMO target proteins and the importance of SUMO isoform specificity.

Pathways from senescence to melanoma: focus on MITF sumoylation

Cutaneous melanoma is a deadly skin cancer that originates from melanocytes. The development of cutaneous melanoma involves a complex interaction between environmental factors, mainly ultraviolet radiation from sunlight, and genetic alterations. Melanoma can also occur from a pre-existing nevus, a benign lesion formed from melanocytes harboring oncogenic mutations that trigger proliferative arrest and senescence entry. Senescence is a potent barrier against tumor progression. As such, the acquisition of mutations that suppress senescence and promote cell division is mandatory for cancer development. This topic appears central to melanoma development because, in humans, several somatic and germline mutations are related to the control of cellular senescence and proliferative activity. Consequently, primary melanoma can be viewed as a paradigm of senescence evasion. In support of this notion, a sumoylation-defective germline mutation in microphthalmia-associated transcription factor (MITF), a master regulator of melanocyte homeostasis, is associated with the development of melanoma. Interestingly, this MITF variant has also been recently reported to negatively impact the program of senescence. This article reviews the genetic alterations that have been shown to be involved in melanoma and that alter the process of senescence to favor melanoma development. Then, the transcription factor MITF and its sumoylation-defective mutant are described. How sumoylation misregulation can change MITF activity and impact the process of senescence is discussed. Finally, the contribution of such information to the development of anti-malignant melanoma strategies is evaluated.