The outer membrane protein, OMP71, of Riemerella anatipestifer, mediates adhesion and virulence by binding to CD46 in ducks.

The Riemerella anatipestifer bacterium is known to cause infectious serositis in ducklings. Moreover, its adherence to the host's respiratory mucosa is a critical step in pathogenesis. Membrane cofactor protein (MCP; CD46) is a complement regulatory factor on the surface of eukaryotic cell membranes. Bacteria have been found to bind to this protein on host cells. Outer membrane proteins (OMPs) are necessary for adhesion, colonisation, and pathogenicity of Gram-negative bacteria; however, the mechanism by which R. anatipestifer adheres to duck cells remains unclear. In this study, pull-down assays and LC-MS/MS identified eleven OMPs interacting with duck CD46 (dCD46), with OMP71 exhibiting the strongest binding. The ability of an omp71 gene deletion strain to bind dCD46 is weaker than that of the wild-type strain, suggesting that this interaction is important. Further evidence of this interaction was obtained by synthesising OMP71 using an Escherichia coli recombinant protein expression system. Adhesion and invasion assays and protein and antibody blocking assays confirmed that OMP71 promoted the R. anatipestifer YM strain (RA-YM) adhesion to duck embryo fibroblasts (DEFs) by binding to CD46. Tests of the pathogenicity of a Δomp71 mutant strain of RA-YM on ducks compared to the wild-type parent supported the hypothesis that OMP71 was a key virulence factor of RA-YM. In summary, the finding that R. anatipestifer exploits CD46 to bind to host cells via OMP71 increases our understanding of the molecular mechanism of R. anatipestifer invasion. The finding suggests potential targets for preventing and treating diseases related to R. anatipestifer infection.

Expression and prognosis of DSG-2, CXADR, CD46 in head and neck squamous cell carcinoma.

OBJECTIVES: Investigating the expression and prognostic significance of adenovirus receptors DSG-2, CXADR and CD46 in head and neck cancer. METHODS: 104 patients with HNSCC (77 OPSCC, 27 LSCC) were retrospectively included in the study. Immunohistochemical staining was performed on all selected slides to detect the expression of DSG-2, CXADR, CD46 and the immunoreactive score (IRS) was determined from the number of positively stained tumor cells and their staining intensity. Furthermore, the respective HPV status was determined by immunohistochemical staining against p16 and HPV-PCR. RESULTS: 81.7 % of the tumors showed DSG-2, 34.6 % of the tumors showed CXADR and 57.7 % of the tumors showed CD46 expression. A high DSG-2 IRS correlated significantly with an advanced tumor size (p= 0.003), increased grading (p=0.012) and positive HPV status (p=0.024) in OPSCC. A high CXADR IRS was significantly associated with a positive lymph node status (p= 0.041) in LSCC and an advanced AJCC stage (p= 0.012) and a positive HPV status (p= 0.009) in OPSCC. No significant correlation could be shown regarding CD46 expression and clinical tumor data. There was no effect of DSG-2, CXADR, and CD46 expression on 5-year overall and on 5-year disease-free survival. CONCLUSION: No prognostic significance of the expression of DSG-2, CXADR or CD46 in HNSCC was seen. DSG-2, CXADR and CD46 are expressed in HNSCC, so that optimization of oncotherapy with adenoviral vectors appears promising. Due to the significantly increased expression of DSG-2 and CXADR in advanced OPSCC tumors, there is potential for optimizing oncotherapy here in particular.

Feasibility study of ADCs targeting TROP-2, HER2, and CD46 in Ductal Adenocarcinoma and Intraductal Carcinoma of the prostate.

BACKGROUND: Ductal Adenocarcinoma (DAC) and Intraductal Carcinoma of the Prostate (IDC-P) respond poorly to all the currently available conventional therapies. Given their accurate and efficient elimination of cancer cells, Antibody-Drug Conjugates (ADCs) have become one of the most promising anticancer treatments. However, no ADCs have so far been approved for Prostate Cancer (PCa) treatment. This study investigated TROP-2, HER2, and CD46 expression in DAC/IDC-P samples, indirectly analyzing their preliminary feasibility as therapeutic targets for future treatment of the two conditions. PATIENTS AND METHODS: We conducted a retrospective study involving 184 participants (87 DAC/IDC-P patients and 97 Prostatic Acinar Adenocarcinoma (PAC) patients with a Gleason score ≥ 8) without prior treatment between August 2017 and August 2022. Immunohistochemical staining was employed to detect the differential protein expressions of TROP-2, HER2, and CD46 in DAC/IDC-P, PAC, and normal prostate tissues. RESULTS: Compared to pure PAC tissues, TROP-2 expression was significantly higher in DAC/IDC-P and DAC/IDC-P-adjacent PAC tissues (H-score 68.8 vs. 43.8, p < 0.001, and 59.8 vs. 43.8, p = 0.022, respectively). No significant differences in HER2 expression were observed across different cancer tissues. Compared to both DAC/IDC-P-adjacent PAC and pure PAC tissues, CD46 expression was significantly higher in DAC/IDC-P tissues (42.3 vs. 28.6, p = 0.041, and 42.3 vs. 24.3, p = 0.0035, respectively). CONCLUSIONS: Herein, TROP-2 and CD46 expression was higher in DAC/IDC-P tissues than in pure PAC and normal prostate tissues. This finding implies that ADCs targeting the two proteins hold significant promise as potential future treatments for DAC/IDC-P.

Complement regulatory protein CD46 promotes bladder cancer metastasis through activation of MMP9.

CD46, a transmembrane protein known for protecting cells from complement­mediated damage, is frequently dysregulated in various types of cancer. Its overexpression in bladder cancers safeguards the cancer cells against both complement and antibody­mediated cytotoxicity. The present study explored a new role of CD46 in facilitating cancer cell invasion and metastasis, examining its regulatory effect on matrix metalloproteases (MMPs) and their effect on the metastatic capability of bladder cancer cells. Specifically, CD46 alteration positively influenced MMP9 expression, but not MMP2, in several bladder cancer cell lines. Furthermore, CD46 overexpression triggered phosphorylation of p38 MAPK and protein kinase B (AKT), leading to enhanced activator protein 1 (AP­1) activity via c­Jun upregulation. The inhibition of p38 or AKT pathways attenuated the CD46­induced MMP9 and AP­1 upregulation, indicating that the promotion of MMP9 by CD46 involved activating both p38 MAPK and AKT. Functionally, the upregulation of MMP9 by CD46 translated to increased migratory and invasive capabilities of bladder cancer cells, as well as enhanced in vivo metastasis. Overall, the present study revealed a novel role for CD46 as a metastasis promoter through MMP9 activation in bladder cancers and highlighted the regulatory mechanism of CD46­mediated MMP9 promotion via p38 MAPK and AKT activation.

CD46 and CD59 inhibitors enhance complement-dependent cytotoxicity of anti-CD38 monoclonal antibodies daratumumab and isatuximab in multiple myeloma and other B-cell malignancy cells.

Multiple myeloma (MM) is an incurable malignancy of the B-cell lineage. Remarkable progress has been made in the treatment of MM with anti-CD38 monoclonal antibodies such as daratumumab and isatuximab, which can kill MM cells by inducing complement-dependent cytotoxicity (CDC). We showed that the CDC efficacy of daratumumab and isatuximab is limited by membrane complement inhibitors, including CD46 and CD59, which are upregulated in MM cells. We recently developed a small recombinant protein, Ad35K++, which is capable of transiently removing CD46 from the cell surface. We also produced a peptide inhibitor of CD59 (rILYd4). In this study, we tested Ad35K++ and rILYd4 in combination with daratumumab and isatuximab in MM cells as well as in cells from two other B-cell malignancies. We showed that Ad35K++ and rILYd4 increased CDC triggered by daratumumab and isatuximab. The combination of both inhibitors had an additive effect in vitro in primary MM cells as well as in vivo in a mouse xenograft model of MM. Daratumumab and isatuximab treatment of MM lines (without Ad35K++ or rILYd4) resulted in the upregulation of CD46/CD59 and/or survival of CD46high/CD59high MM cells that escaped the second round of daratumumab and isatuximab treatment. The escape in the second treatment cycle was prevented by the pretreatment of cells with Ad35K++. Overall, our data demonstrate that Ad35K++ and rILYd4 are efficient co-therapeutics of daratumumab and isatuximab, specifically in multi-cycle treatment regimens, and could be used to improve treatment of multiple myeloma.

Computational Analysis of CD46 Protein Interaction with SARS-CoV-2 Structural Proteins: Elucidating a Putative Viral Entry Mechanism into Human Cells.

This study examines an unexplored aspect of SARS-CoV-2 entry into host cells, which is widely understood to occur via the viral spike (S) protein's interaction with human ACE2-associated proteins. While vaccines and inhibitors targeting this mechanism are in use, they may not offer complete protection against reinfection. Hence, we investigate putative receptors and their cofactors. Specifically, we propose CD46, a human membrane cofactor protein, as a potential putative receptor and explore its role in cellular invasion, acting possibly as a cofactor with other viral structural proteins. Employing computational techniques, we created full-size 3D models of human CD46 and four key SARS-CoV-2 structural proteins-EP, MP, NP, and SP. We further developed 3D models of CD46 complexes interacting with these proteins. The primary aim is to pinpoint the likely interaction domains between CD46 and these structural proteins to facilitate the identification of molecules that can block these interactions, thus offering a foundation for novel pharmacological treatments for SARS-CoV-2 infection.

CD46 expression in the central nervous system of male and female pubescent mice.

CD46 is a complementary regulatory protein ubiquitously expressed in human cells, controlling complement system activation. CD46 has further been identified to have several other functions including regulatory T cell induction and intestinal epithelial (IEC) barrier regulation. Activation of CD46 in the IEC can impact intestinal barrier permeability and immune system functioning. CD46 has only been identified in the spermatozoa and retina of mice. In other murine cells, the homologue CRRY is identified to function as the complementary regulator. Due to the identification of CRRY across other wild-type mouse cells and the development of mouse strains transgenic for human CD46, no recent research has been conducted to determine if CD46 is present in non-transgenic mouse strains. Therefore, the current study investigated if CD46 is expressed in the substantia nigra (SN) and caudate putamen (CP) of pubescent CD1 mice and examined the acute effects of pubertal antimicrobial and lipopolysaccharide (LPS) treatment on CD46 expression in the brain. As of 5 weeks of age, mice were administered mixed antimicrobial solution or water with oral gavage twice daily for 7 days. At 6 weeks of age, mice received an intraperitoneal injection of LPS or saline. Mice were euthanized 8 h post-injection and brain samples were collected. Our results indicate that pubescent CD-1 mice express CD46 in the SN and CP. However, LPS-treated mice displayed significantly less CD46 expression in the SN in comparison to saline-treated mice. Furthermore, males displayed more CD46 in the CP compared to females, regardless of LPS and antimicrobial treatments. Our data suggest CD46 is present in CD1 mice and that LPS and antimicrobial treatments impact CD46 protein expression in a sex-dependent manner. These results have important implications for the expression of CD46 in the mouse brain and the understanding of its role in immune system regulation.

Toward the understanding of DSG2 and CD46 interaction with HAdV-11 fiber, a super-complex analysis.

IMPORTANCE: The main limitation of oncolytic vectors is neutralization by blood components, which prevents intratumoral administration to patients. Enadenotucirev, a chimeric HAdV-11p/HAdV-3 adenovirus identified by bio-selection, is a low seroprevalence vector active against a broad range of human carcinoma cell lines. At this stage, there's still some uncertainty about tropism and primary receptor utilization by HAdV-11. However, this information is very important, as it has a direct influence on the effectiveness of HAdV-11-based vectors. The aim of this work is to determine which of the two receptors, DSG2 and CD46, is involved in the attachment of the virus to the host, and what role they play in the early stages of infection.

miR-132-3p regulates antibody-mediated complement-dependent cytotoxicity in colon cancer cells by directly targeting CD55.

The overexpression of membrane-bound complement regulatory proteins (mCRPs) on tumour cells helps them survive complement attacks by suppressing antibody-mediated complement-dependent cytotoxicity (CDC). Consequently, mCRP overexpression limits monoclonal antibody drug immune efficacy. CD55, an mCRP, plays an important role in inhibiting antibody-mediated CDC. However, the mechanisms regulating CD55 expression in tumour cells remain unclear. Here, the aim was to explore CD55-targeting miRNAs. We previously constructed an in vitro model comprising cancer cell lines expressing α-gal and serum containing natural antibodies against α-gal and complement. This was used to simulate antibody-mediated CDC in colon cancer cells. We screened microRNAs that directly target CD55 using LoVo and Ls-174T colon cell lines, which express CD55 at low and high levels, respectively. miR-132-3p expression was dramatically lower in Ls-174T cells than in LoVo cells. miR-132-3p overexpression or inhibition transcriptionally regulated CD55 expression by specifically targeting its mRNA 3'-untranslated regions. Further, miR-132-3p modulation regulated colon cancer cell sensitivity to antibody-mediated CDC through C5a release and C5b-9 deposition. Moreover, miR-132-3p expression was significantly reduced, whereas CD55 expression was increased, in colon cancer tissues compared to levels in adjacent normal tissues. CD55 protein levels were negatively correlated with miR-132-3p expression in colon cancer tissues. Our results indicate that miR-132-3p regulates colon cancer cell sensitivity to antibody-mediated CDC by directly targeting CD55. In addition, incubating the LoVo human tumour cell line, stably transfected with the xenoantigen α-gal, with human serum containing natural antibodies comprises a stable and cheap in vitro model to explore the mechanisms underlying antibody-mediated CDC.

Knockdown of membrane-bound complement regulatory proteins suppresses colon cancer growth in mice through inducing tumor cell apoptosis.

CD46, CD55 and CD59 are membrane-bound complement regulatory proteins (mCRPs) and highly expressed in many tumor tissues. Our analysis by RNA sequencing and qRT-PCR revealed that the expression of mCRPs was significantly elevated in cancer tissues of 15 patients with colon cancer. To further investigate the role of mCRPs in the development of colon cancer, we suppressed the expression of mCRPs by CD46-shRNA, CD55-shRNA and CD59-shRNA in colon cancer cell lines, SW620 and HT-29 cells. The results indicated that CD46-shRNA, CD55-shRNA and CD59-shRNA effectively reduced the expression of mCRPs, accompanied with the increased LDH release and the percentage of Annexin V + 7-AAD- early phase of apoptotic cells. The similar cytotoxic effects were also observed in the cells treated with CD46 neutralizing antibody (aCD46), associated with the increased C5b-9 deposition, cleaved caspase-3 and Bax expression in the treated cells. The cytotoxic effects by mCRPs knock-down were potentiated in the cells co-treated with doxorubicin (Dox). In addition, STAT3, STAT6, and p38 MAPK inhibitors, including C188-9, AS1517499 and SB203580 effectively reduced the expression of CD46 in the treated colon cells, associated with increased cell apoptosis and LDH release. Further study with mouse model revealed that mCRPs knockdown by mCRPs-shRNA significantly reduced colon cancer growth, associated with increased expression of Bax, cleaved caspase-3 and C5b-9 deposition, but reduced expression of Bcl-2, IL-6 and IL-1beta in tumor tissues of nude mice transplanted with SW620 cells. Thereby, mCRPs expression in human colon cancer cells were upregulated by STAT3/STAT6/p38 MAPK signaling and mCRPs knockdown reduced colon cancer growth in mice through inducing tumor cell apoptosis.

Relationship between the expression of complement inhibitory proteins and therapeutic efficacy of antibodies in breast cancer.

Complement regulatory proteins (mCRPs) CD55, CD46 and CD59 have been proposed as key elements in therapeutic resistance against cancer. mCRP-expressing tumor cells, in addition to hindering trastuzumab, pertuzumab and sacituzumab-govitecan therapeutic activity in breast cancer, can regulate biological processes that promote tumor progression. This review describes the structure of mCRPs and analyzes their expression using transcriptomic databases from breast cancer patients, in addition to collecting information on mCRPs interactions and signaling in tumor cells. Given that mCRPs are relevant targets, several strategies that have been explored for their inhibition and regulation in order to increase therapeutic efficacy and prevent cancer resistance and progression are described.

Se ha propuesto a las proteínas reguladoras de complemento (mCRP) CD55, CD46 y CD59 como piezas clave en la resistencia terapéutica contra el cáncer. Las células tumorales que expresan las mCRP, además de obstaculizar la actividad terapéutica de trastuzumab, pertuzumab y sacituzumab-govitecan en cáncer de mama, pueden regular procesos biológicos que promueven la progresión tumoral. Esta revisión describe la estructura de las mCRP y analiza su expresión a partir de bases de datos transcriptómicos de pacientes con cáncer de mama; también recopila información de interacciones y señalización de las mCRP en células tumorales. Dado que estas mCRP son dianas relevantes, se describen diversas estrategias para su inhibición y regulación para incrementar la eficacia terapéutica y evitar la resistencia y progresión del cáncer.

CD46 Isoforms Influence the Mode of Entry by Human Herpesvirus 6A/B in T Cells.

CD46 is a receptor for human herpesvirus 6A (HHV-6A) and is in some cells also important for infection with HHV-6B. CD46 has several isoforms of which the most commonly expressed can be distinguished by expression of a BC domain or a C domain in a serine-threonine-proline-rich (STP) extracellular region. Using a SupT1 CD46 CRISPR-Cas9 knockout model system reconstituted with specific CD46 isoforms, we demonstrated that HHV-6A infection was more efficient when BC isoforms were expressed as opposed to C isoforms, measured by higher levels of intracellular viral transcripts and recovery of more progeny virus. Although the B domain contains several O-glycosylations, mutations of Ser and Thr residues did not prevent infection with HHV-6A. The HHV-6A infection was blocked by inhibitors of clathrin-mediated endocytosis. In contrast, infection with HHV-6B was preferentially promoted by C isoforms mediating fusion-from-without, and this infection was less affected by inhibitors of clathrin-mediated endocytosis. Taken together, HHV-6A preferred BC isoforms, mediating endocytosis, whereas HHV-6B preferred C isoforms, mediating fusion-from-without. This demonstrates that the STP region of CD46 is important for regulating the mode of infection in SupT1 cells and suggests an epigenetic regulation of the host susceptibility to HHV-6A and HHV-6B infection. IMPORTANCE CD46 is the receptor used by human herpesvirus 6A (HHV-6A) during infection of T cells, but it is also involved in infection of certain T cells by HHV-6B. The gene for CD46 allows expression of several variants of CD46, known as isoforms, but whether the isoforms matter for infection of T cells is unknown. We used a genetic approach to delete CD46 from T cells and reconstituted them with separate isoforms to study them individually. We expressed the isoforms known as BC and C, which are distinguished by the potential inclusion of a B domain in the CD46 molecule. We demonstrate that HHV-6A prefers the BC isoform to infect T cells, and this occurs predominantly by clathrin-mediated endocytosis. In contrast, HHV-6B prefers the C isoform and infects predominantly by fusion-from-without. Thus, CD46 isoforms may affect susceptibility of T cells to infection with HHV-6A and HHV-6B.

Lupus nephritis with corticosteroid responsiveness: molecular changes of CD46-mediated type 1 regulatory T cells.

BACKGROUND: The engagement of the complement regulatory proteins CD46 and CD3 in human CD4+ T cells induces the type 1 regulatory T cells (Tr1) and interleukin-10 (IL-10) secretion. This study aimed to elucidate the molecular changes of Tr1 cells through CD46 cytoplasmic Cyt1 tail in lupus nephritis (LN) respond to intravenous methylprednisolone (ivMP) therapy. METHODS: We enrolled 40 pediatric patients with LN and 30 healthy controls. Clinical characteristics and peripheral blood mononuclear cells were collected before and 3 days after the administration of ivMP. Kidney specimens were taken from five LN and five minimal-change nephrotic syndrome patients. RESULTS: We found that defective CD46-mediated T-helper type 1 contraction (IL-10 switching) is present in active LN patients. The ivMP therapy enhanced LN remission, restored the production of IL-10, increased the CD46-Cyt1/Cyt2 ratio, AKT, and cAMP-responsive element-binding protein phosphorylation, and induced migration with the expression of chemokine receptor molecules CCR4, CCR6, and CCR7 of CD3/CD46-activated Tr1 cells. CONCLUSIONS: Pharmacologic interventions that alter the patterns of CD46-Cyt1/Cyt2 expression and the secretion of IL-10 by CD3/CD46-activated Tr1 cells can be used in patients with active LN. IMPACT: In patients with LN, ivMP was associated with increased IL-10 production and increased CD46-Cyt1/Cyt2 ratio and AKT phosphorylation by Tr1 cells, with enhanced potential to migration in response to CCL17. These results suggest that expression levels of CD46 isoforms Cyt1 and Cyt2 in CD4 + CD46 + Tr1 cells differ in patients with active LN but can be corrected by corticosteroid treatment. Enhancing the expression of functional CD4 + CD46 + Tr1 cells may be a useful therapeutic approach for LN.

Different impact of bovine complement regulatory protein 46 (CD46bov) as a cellular receptor for members of the species Pestivirus H and Pestivirus G.

The genus Pestivirus within the family Flaviviridae comprises highly relevant animal pathogens such as bovine viral diarrhoea virus 1 and 2 (BVDV-1 and -2) classified into the two species Pestivirus A and Pestivirus B, respectively. First described in 2004, HoBi-like pestiviruses (HoBiPeV) represent emerging bovine pathogens that belong to a separate species (Pestivirus H), but share many similarities with BVDV-1 and -2. Additionally, two giraffe pestivirus (GPeV) strains both originating from Kenya represent another distinct species (Pestivirus G), whose members replicate very efficiently in bovine cells. In this study, we investigated the role of bovine complement regulatory protein 46 (CD46bov), the receptor of BVDV-1 and -2, in the entry of HoBiPeV and GPeV. For this purpose, bovine CD46-knockout and CD46-rescue cell lines were generated by CRISPR/Cas9 technology and subsequent trans-complementation, respectively. Our results provide strong evidence that the impact of CD46bov differs between viruses belonging to Pestivirus H and viruses representing Pestivirus G: CD46bov revealed to be a major cellular entry factor for HoBiPeV strain HaVi-20. In contrast, GPeV strain PG-2 presented as largely independent of CD46bov, suggesting a different entry mechanism involving other molecular determinants which remain to be identified. In addition, we demonstrated that, similar to BVDV-1 and -2, virus isolates of both Pestivirus H and Pestivirus G are able to adapt to cell culture conditions by using heparan sulfate to enter the host cell. In conclusion, our findings show that different bovine pestiviruses use diverse mechanisms of host cell entry.

Ex Vivo and In Vivo CD46 Receptor Utilization by Species D Human Adenovirus Serotype 26 (HAdV26).

Human adenovirus serotype 26 (Ad26) is used as a gene-based vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and HIV-1. However, its primary receptor portfolio remains controversial, potentially including sialic acid, coxsackie and adenovirus receptor (CAR), integrins, and CD46. We and others have shown that Ad26 can use CD46, but these observations were questioned on the basis of the inability to cocrystallize Ad26 fiber with CD46. Recent work demonstrated that Ad26 binds CD46 with its hexon protein rather than its fiber. We examined the functional consequences of Ad26 for infection in vitro and in vivo. Ectopic expression of human CD46 on Chinese hamster ovary cells increased Ad26 infection significantly. Deletion of the complement control protein domain CCP1 or CCP2 or the serine-threonine-proline (STP) region of CD46 reduced infection. Comparing wild-type and sialic acid-deficient CHO cells, we show that the usage of CD46 is independent of its sialylation status. Ad26 transduction was increased in CD46 transgenic mice after intramuscular (i.m.) injection but not after intranasal (i.n.) administration. Ad26 transduction was 10-fold lower than Ad5 transduction after intratumoral (i.t.) injection of CD46-expressing tumors. Ad26 transduction of liver was 1,000-fold lower than that ofAd5 after intravenous (i.v.) injection. These data demonstrate the use of CD46 by Ad26 in certain situations but also show that the receptor has little consequence by other routes of administration. Finally, i.v. injection of high doses of Ad26 into CD46 mice induced release of liver enzymes into the bloodstream and reduced white blood cell counts but did not induce thrombocytopenia. This suggests that Ad26 virions do not induce direct clotting side effects seen during coronavirus disease 2019 (COVID-19) vaccination with this serotype of adenovirus. IMPORTANCE The human species D Ad26 is being investigated as a low-seroprevalence vector for oncolytic virotherapy and gene-based vaccination against HIV-1 and SARS-CoV-2. However, there is debate in the literature about its tropism and receptor utilization, which directly influence its efficiency for certain applications. This work was aimed at determining which receptor(s) this virus uses for infection and its role in virus biology, vaccine efficacy, and, importantly, vaccine safety.

Circulating Pro-Inflammatory Exosomes Worsen Stroke Outcomes in Aging.

[Figure: see text].

New Insights into Xenotransplantation for Cartilage Repair: Porcine Multi-Genetically Modified Chondrocytes as a Promising Cell Source.

Transplantation of xenogenic porcine chondrocytes could represent a future strategy for the treatment of human articular cartilage defects. Major obstacles are humoral and cellular rejection processes triggered by xenogenic epitopes like α-1,3-Gal and Neu5Gc. Besides knockout (KO) of genes responsible for the biosynthesis of respective epitopes (GGTA1 and CMAH), transgenic expression of human complement inhibitors and anti-apoptotic as well as anti-inflammatory factors (CD46, CD55, CD59, TNFAIP3 and HMOX1) could synergistically prevent hyperacute xenograft rejection. Therefore, chondrocytes from different strains of single- or multi-genetically modified pigs were characterized concerning their protection from xenogeneic complement activation. Articular chondrocytes were isolated from the knee joints of WT, GalTKO, GalT/CMAH-KO, human CD59/CD55//CD46/TNFAIP3/HMOX1-transgenic (TG), GalTKO/TG and GalT/CMAHKO/TG pigs. The tissue-specific effectiveness of the genetic modifications was tested on gene, protein and epitope expression level or by functional assays. After exposure to 20% and 40% normal human serum (NHS), deposition of C3b/iC3b/C3c and formation of the terminal complement complex (TCC, C5b-9) was quantified by specific cell ELISAs, and generation of the anaphylatoxin C5a by ELISA. Chondrocyte lysis was analyzed by Trypan Blue Exclusion Assay. In all respective KO variants, the absence of α -1,3-Gal and Neu5Gc epitope was verified by FACS analysis. In chondrocytes derived from TG animals, expression of CD55 and CD59 could be confirmed on gene and protein level, TNFAIP3 on gene expression level as well as by functional assays and CD46 only on gene expression level whereas transgenic HMOX1 expression was not evident. Complement activation in the presence of NHS indicated mainly effective although incomplete protection against C3b/iC3b/C3c deposition, C5a-generation and C5b-9 formation being lowest in single GalTKO. Chondrocyte viability under exposure to NHS was significantly improved even by single GalTKO and completely preserved by all other variants including TG chondrocytes without KO of xenoepitopes.

C646 inhibits G2/M cell cycle-related proteins and potentiates anti-tumor effects in pancreatic cancer.

The activity of histone acetyltransferases (HATs) plays a central role in an epigenetic modification in cooperation with HDACs (histone deacetyl transferases). It is likely that malfunction of this enzymatic machinery controlling epigenetic modification is relevant to carcinogenesis and tumor progression. However, in pancreatic cancer, the clinical relevance of HAT activity and histone acetylation has remained unclear. We identified that H3 acetylation was expressed in all pancreatic cancer patients, indicating that H3 acetylation may be essential in pancreatic cancer cells. We also found that the HAT inhibitor C646 augmented anti-tumor effects in vitro by inhibiting cell proliferation and cell cycle progression concomitantly with suppression of acetylated H3K9 and H3K27 expression. C646 or p300 and CBP (CREB-binding protein)-specific siRNA treatment inhibited the transcription of the G2/M cell cycle regulatory proteins cyclin B1 and CDK1 (cyclin-dependent kinase 1). C646 treatment also inhibited tumor growth in vivo in a xenograft mouse model. C646 could be an effective therapeutic agent for pancreatic cancer. The epigenetic status of pancreatic cancers based on their level of histone H3 acetylation may influence patient survival. Epigenetic stratification according to H3K27 acetylation could be useful for predicting disease prognosis as well as the therapeutic efficacy of C646 in pancreatic cancer.

Membrane cofactor protein (MCP; CD46): deficiency states and pathogen connections.

Membrane cofactor protein (MCP; CD46), a ubiquitously expressed complement regulatory protein, serves as a cofactor for serine protease factor I to cleave and inactivate C3b and C4b deposited on host cells. However, CD46 also plays roles in human reproduction, autophagy, modulating T cell activation and effector functions and is a member of the newly identified intracellular complement system (complosome). CD46 also is a receptor for 11 pathogens ('pathogen magnet'). While CD46 deficiencies contribute to inflammatory disorders, its overexpression in cancers and role as a receptor for some adenoviruses has led to its targeting by oncolytic agents and adenoviral-based therapeutic vectors, including coronavirus disease of 2019 (COVID-19) vaccines. This review focuses on recent advances in identifying disease-causing CD46 variants and its pathogen connections.

Microglial trogocytosis and the complement system regulate axonal pruning in vivo.

Partial phagocytosis-called trogocytosis-of axons by microglia has been documented in ex vivo preparations but has not been directly observed in vivo. The mechanisms that modulate microglial trogocytosis of axons and its function in neural circuit development remain poorly understood. Here, we directly observe axon trogocytosis by microglia in vivo in the developing Xenopus laevis retinotectal circuit. We show that microglia regulate pruning of retinal ganglion cell axons and are important for proper behavioral response to dark and bright looming stimuli. Using bioinformatics, we identify amphibian regulator of complement activation 3, a homolog of human CD46, as a neuronally expressed synapse-associated complement inhibitory molecule that inhibits trogocytosis and axonal pruning. Using a membrane-bound complement C3 fusion protein, we demonstrate that enhancing complement activity enhances axonal pruning. Our results support the model that microglia remodel axons via trogocytosis and that neurons can control this process through expression of complement inhibitory proteins.