KSHV downregulation of galectin-3 in Kaposi's sarcoma

The Multifaceted Roles of Galectins in Host-Virus Interactions: A Comprehensive Overview

Galectins are a family of β-galactosides-binding protein, crucial regulators of host-virus interactions. They achieve this by recognizing specific glycan patterns on viral surfaces or mediating interactions with intracellular viral or host proteins, subsequently influencing the critical phases of the viral life cycle, such as attachment, replication, immune evasion, and reactivation. Furthermore, galectins modulate host immune responses, shaping the progression and outcomes of viral infections. This review comprehensively examines the roles of both endogenous and exogenous galectins in viral infections, noting that only a few galectins, including Galectin-1, -3, -4, -7, -8, and -9, Have been identified as key players in viral infection. Notably, Galectin-1, -3, and -9 play diverse functions in both DNA and RNA viral infection. Emerging evidence highlights the potential of Galectin-4 and -8 as intracellular sensors and modulators of viral pathogenesis. Endogenous galectins, produced by host cells, act through both glycan-dependent and glycan-independent mechanisms, influencing viral processes and immune responses. Exogenous galectins, which are secreted by other cells or administered as recombinant proteins, can either enhance or counteract the actions of endogenous galectins. The functions of galectins are virus-specific and context-dependent, serving as either promoters or inhibitors of viral replication and reactivation. Dysregulation of galectin expression is often linked to disease progression, highlighting their potential as diagnostic and prognostic biomarkers, as well as therapeutic targets. The important and varied roles that galectins play in viral infections are highlighted in this review, which also provides fresh insights into host-pathogen interactions and the development of antiviral tactics.

HIGHLIGHTS

Galectins and Host-Pathogen Interactions: The roles in viral infections

Galectins, a family of carbohydrate-binding proteins, play crucial roles in the host-virus interaction landscape. This review explores the multifaceted contributions of endogenous galectins to various stages of the viral lifecycle, including attachment, replication, assembly, and release of progeny virions. Recent studies have indicated that viral infections can induce the expression and secretion of specific galectins, with elucidated signaling pathways in some cases, enhancing our understanding of their regulatory mechanisms. While many studies have focused on the effects of exogenous recombinant galectins, there is growing interest in the intrinsic functions of endogenous galectins, particularly through genetic alterations in cellular models. This review highlights the need for further research to uncover the complex roles of galectins in modulating viral infections and emphasizes their potential as therapeutic targets in the fight against viral diseases. Understanding these interactions could pave the way for novel strategies to enhance host defense mechanisms and mitigate viral pathogenesis.

The Pivotal Role of Galectin-3 in Viral Infection: A Multifaceted Player in Host-Pathogen Interactions

Galectin-3 (Gal-3), a beta-galactoside-binding lectin, plays a pivotal role in various cellular processes, including immune responses, inflammation, and cancer progression. This comprehensive review aims to elucidate the multifaceted functions of Gal-3, starting with its crucial involvement in viral entry through facilitating viral attachment and catalyzing internalization. Furthermore, Gal-3 assumes significant roles in modulating immune responses, encompassing the activation and recruitment of immune cells, regulation of immune signaling pathways, and orchestration of cellular processes such as apoptosis and autophagy. The impact of Gal-3 extends to the viral life cycle, encompassing critical phases such as replication, assembly, and release. Notably, Gal-3 also contributes to viral pathogenesis, demonstrating involvement in tissue damage, inflammation, and viral persistence and latency elements. A detailed examination of specific viral diseases, including SARS-CoV-2, HIV, and influenza A, underscores the intricate role of Gal-3 in modulating immune responses and facilitating viral adherence and entry. Moreover, the potential of Gal-3 as a biomarker for disease severity, particularly in COVID-19, is considered. Gaining further insight into the mechanisms and roles of Gal-3 in these infections could pave the way for the development of innovative treatment and prevention options for a wide range of viral diseases.

Molecular Identification and mRNA Expression Profiles of Galectin-9 Gene in Red Sea Bream (Pagrus major) Infected with Pathogens

Galectin (Gal) is a member of a family of β-galactoside-binding lectin. The members of this family play important roles in the recognition of carbohydrate ligands and in various other biological processes. In this study, we identified the gene encoding Gal-9 in Pagrus major (PmGal-9) and analyzed its expression in various tissues after pathogen challenge. Alignment analysis revealed that the two galactose-binding lectin domains of the deduced protein were highly conserved among all the teleosts. Phylogenetic analysis revealed that PmGal-9 is most closely related to the Gal-9 gene of gilthead sea bream. PmGal-9 was ubiquitously expressed in all tissues analyzed but was predominantly expressed in the spleen, head kidney, and intestine. After challenges with major microbial pathogens (Edwardsiella piscicida, Streptococcus iniae, or red sea bream iridovirus) of red sea bream, PmGal-9 mRNA expression was significantly regulated in most immune-related tissues. These results suggested that PmGal-9 not only plays an important role in the immune system of red sea bream but is also a possible inflammatory marker for pathogenic diseases.

The role of galectins in virus infection - A systemic literature review

BACKGROUND

Galectins are β-Galactose binding lectins expressed in numerous cells and play multiple roles in various physiological and cellular functions. However, few information is available regarding the role of galectins in virus infections. Here, we conducted a systemic literature review to analyze the role of galectins in human virus infection.

METHODS

This study uses a systematic method to identify and select eligible articles according to the PRISMA guidelines. References were selected from PubMed, Web of Science and Google Scholar database covering publication dated from August 1995 to December 2018.

RESULTS

Results indicate that galectins play multiple roles in regulation of virus infections. Galectin-1 (Gal-1), galectin-3 (Gal-3), galectin-8 (Gal-8), and galectin-9 (Gal-9) were found as the most predominant galectins reported to participate in virus infection. The regulatory function of galectins occurs by extracellularly binding to viral glycosylated envelope proteins, interacting with ligands or receptors on immune cells, or acting intracellularly with viral or cellular components in the cytoplasm. Several galectins express either positive or negative regulatory role, while some had dual regulatory capabilities on virus propagation based on the conditions and their localization. However, limited information about the endogenous function of galectins were found. Therefore, the endogenous effects of galectins in host-virus regulation remains valuable to investigate.

CONCLUSIONS

This study offers information regarding the various roles galectins shown in viral infection and suggest that galectins can potentially be used as viral therapeutic targets or antagonists.

Gal power: the diverse roles of galectins in regulating viral infections

Viruses, as a class of pathogenic microbe, remain a significant health burden globally. Viral infections result in significant morbidity and mortality annually and many remain in need of novel vaccine and anti-viral strategies. The development of effective novel anti-viral therapeutics, in particular, requires detailed understanding of the mechanism of viral infection, and the host response, including the innate and adaptive arms of the immune system. In recent years, the role of glycans and lectins in pathogen-host interactions has become an increasingly relevant issue. This review focuses on the interactions between a specific lectin family, galectins, and the broad range of viral infections in which they play a role. Discussed are the diverse activities that galectins play in interacting directly with virions or the cells they infect, to promote or inhibit viral infection. In addition we describe how galectin expression is regulated both transcriptionally and post-transcriptionally by viral infections. We also compare the contribution of known galectin-mediated immune modulation, across a range of innate and adaptive immune anti-viral responses, to the outcome of viral infections.

Disrupting galectin-1 interactions with N-glycans suppresses hypoxia-driven angiogenesis and tumorigenesis in Kaposi's sarcoma

Disrupting Gal-1 interactions with N-glycans prevents hypoxia-driven angiogenesis to suppress tumorigenesis of Kaposi’s sarcoma

Kaposi’s sarcoma (KS), a multifocal vascular neoplasm linked to human herpesvirus-8 (HHV-8/KS-associated herpesvirus [KSHV]) infection, is the most common AIDS-associated malignancy. Clinical management of KS has proven to be challenging because of its prevalence in immunosuppressed patients and its unique vascular and inflammatory nature that is sustained by viral and host-derived paracrine-acting factors primarily released under hypoxic conditions. We show that interactions between the regulatory lectin galectin-1 (Gal-1) and specific target N-glycans link tumor hypoxia to neovascularization as part of the pathogenesis of KS. Expression of Gal-1 is found to be a hallmark of human KS but not other vascular pathologies and is directly induced by both KSHV and hypoxia. Interestingly, hypoxia induced Gal-1 through mechanisms that are independent of hypoxia-inducible factor (HIF) 1α and HIF-2α but involved reactive oxygen species–dependent activation of the transcription factor nuclear factor κB. Targeted disruption of Gal-1–N-glycan interactions eliminated hypoxia-driven angiogenesis and suppressed tumorigenesis in vivo. Therapeutic administration of a Gal-1–specific neutralizing mAb attenuated abnormal angiogenesis and promoted tumor regression in mice bearing established KS tumors. Given the active search for HIF-independent mechanisms that serve to couple tumor hypoxia to pathological angiogenesis, our findings provide novel opportunities not only for treating KS patients but also for understanding and managing a variety of solid tumors.

Identifying dysregulated genes induced by Kaposi's sarcoma-associated herpesvirus (KSHV)

Currently KS is the most predominant HIV/AIDS related malignancy in Southern Africa and hence the world. It is characterized as an angioproliferative tumor of vascular endothelial cells and produces rare B cell lymphoproliferative diseases in the form of pleural effusion lymphomas (PEL) and some forms of multicentric Castleman's disease. Only 1-5% of cells in KS lesions actively support lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV), the etiological agent associated with KS, and it is clear that cellular factors must interact with viral factors in the process of oncogenesis and tumor progression. Identifying novel host-factor determinants which contribute to KS pathology is essential for developing prognostic markers for tumor progression and metastasis as well as for developing novel therapeutics for the treatment of KS. The accompanying video details the methods we use to identify host cell gene expression programs altered in dermal microvascular endothelial cells (DMVEC) after KSHV infection and in KS tumor tissue. Once dysregulated genes are identified by microarray analysis, changes in protein expression are confirmed by immunoblot and dual labeled immunofluorescence. Changes in transcriptional expression of dysregulated genes are confirmed in vitro by quantitative real-time polymerase chain reaction (qRT-PCR). Validation of in vitro findings using archival KS tumor tissue is also performed by dual labeled immunochemistry and tissue microarrays. Our approach to identifying dysregulated genes in the KS tumor tissue microenvironment will allow the development of in vitro and subsequently in vivo model systems for discovery and evaluation of potential novel therapeutic for the treatment of KS.