Biology subjects

Marstad, A.

Publications and source records attributed to Marstad, A..

5 recordsLinked to original sources

bioRxiv2026

Prostaglandin E2 facilitates reciprocal crosstalk between intestinal smooth muscle tissue and epithelium in tumor development

Colorectal cancer arises from intestinal epithelial cells and is driven by the accumulation of aberrant signaling events that disrupt intestinal stem cell (ISC) homeostasis. While stromal regulation of the ISC niche is increasingly recognized, the contribution of the underlying/adjacent smooth muscle tissue (SMT) remains poorly characterized. In particular, the potential crosstalk between normal or tumoral epithelium and the SMT is largely unexplored. Here, we investigate the ability of the SMT in modulating normal and tumorigenic epithelial biology, and the impact of the tumoral epithelium on the underlying SMT. Mechanistically, by using imaging analyses, transcriptomics, and mass spectrometry, we identify the SMT-derived factor Prostaglandin E2 (PGE2) as the key driver of epithelial dedifferentiation, promoting YAP transcriptional activation, organoid enlargement, and spheroid morphology in intestinal epithelial organoids following SMT supernatant exposure. Conversely, we show that non-invasive tumoral epithelium induces significant changes in the underlying SMT. Tumor-associated SMT shows structural remodeling, inflammation, and reduced muscle fitness. Furthermore, we detected increased prostaglandin signaling, including upregulation of PGE2 synthase Ptgs1 (COX1), in the SMT underneath the epithelial tumor. Our results reveal a communication between the tumoral epithelium and the underlying SMT prior to metastasis, which could be a facilitating step for tumoral extramural progression. Taken together, these findings highlight a novel tumor-stroma interaction.

Molecular Biology↗

bioRxiv2025

NINJ1 is activated by Mycobacterium tuberculosis ESX-1 secreted effector EsxA and mediates necrosis of infected human macrophages

Lytic cell death contributes to tissue damage and dissemination during Mycobacterium tuberculosis (Mtb) infection, yet the mechanisms governing plasma membrane rupture (PMR) remain incompletely defined. Here, we identify Ninjurin-1 (NINJ1), a mediator of PMR, as a central effector of macrophage lysis during Mtb infection. Mtb infection induced NINJ1 oligomerization, and genetic deletion or pharmacological inhibition of NINJ1 markedly reduced lactate dehydrogenase (LDH) release. Cytokine secretion was largely preserved in NINJ1-deficient macrophages, with the exception of CXCL10. Unexpectedly, inhibition of pyroptosis, apoptosis, necroptosis, and ferroptosis - individually or in combination - did not prevent NINJ1 activation or PMR, indicating that Mtb-induced membrane rupture proceeds independently of canonical regulated cell death pathways. However, NINJ1 oligomerization and PMR required the Mtb ESX-1 secretion system, identifying a bacterial virulence determinant as a critical upstream trigger. Although osmoprotective PEG partially reduced LDH release, neither calcium signaling nor cell swelling accounted for NINJ1-dependent PMR in Mtb-infected macrophages. Together, these findings establish NINJ1 as a key executioner of Mtb-induced lytic cell death and reveal an ESX-1-dependent pathway of PMR that is uncoupled from canonical host cell death programs. TeaserNINJ1 mediates plasma membrane rupture of macrophages infected with Mycobacterium tuberculosis

microbiology↗

bioRxiv2019

Plasma membrane damage causes NLRP3 activation and pyroptosis during Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb) is a major global health problem and causes extensive cytotoxicity in patient cells and tissues. Here we define an NLRP3, caspase-1 and gasdermin D-mediated pathway to pyroptosis in human monocytes following exposure to Mtb. We demonstrate an ESX-1 mediated, contact-induced plasma membrane (PM) damage response that occurs during phagocytosis or from the cytosolic side of the PM after phagosomal rupture in Mtb infected cells. This PM injury in turn causes K+ efflux and activation of NLRP3 dependent IL-1{beta} release and pyroptosis, facilitating the spread of Mtb to neighbouring cells. Further we reveal a dynamic interplay of pyroptosis with ESCRT-mediated PM repair. Collectively, these findings reveal a novel mechanism for pyroptosis and spread of infection acting through dual PM disturbances both during and after phagocytosis. We also highlight dual PM damage as a common mechanism utilized by other NLRP3 activators that have previously been shown to act through lysosomal damage.\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC=\"FIGDIR/small/747014v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (28K):\norg.highwire.dtl.DTLVardef@1911356org.highwire.dtl.DTLVardef@18c99dcorg.highwire.dtl.DTLVardef@1c94bb9org.highwire.dtl.DTLVardef@8a69db_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2019

Global assessment of Mycobacterium avium subspecies hominissuis genetic requirement for growth and virulence.

Nontuberculous mycobacterial infections caused by the opportunistic pathogen Mycobacterium avium subsp. hominissuis (MAH) are currently receiving renewed attention due to increased incidence combined with difficult treatment. Insights into the disease-causing mechanisms of this species have been hampered by difficulties in genetic manipulation of the bacteria. Here, we identified and sequenced a highly transformable, virulent MAH clinical isolate susceptible to high-density transposon mutagenesis, facilitating global gene disruption and subsequent investigation of MAH gene function. By transposon insertion sequencing (TnSeq) of this strain, we defined the MAH genome-wide genetic requirement for virulence and in vitro growth, and organized ~3500 identified transposon mutants for hypothesis-driven research. The majority (71 %) of the genes we identified as essential for MAH in vitro had a growth-essential mutual ortholog in the related and highly virulent M. tuberculosis (Mtb). However, passaging our library through a mouse model of infection revealed a substantial number (54% of total hits) of novel virulence genes. Strikingly, > 97 % of the MAH virulence genes had a mutual ortholog in Mtb. Two of the three virulence genes specific to MAH (i.e. no Mtb mutual orthologs) were PPE proteins, a family of proteins unique to mycobacteria and highly associated with virulence. Finally, we validated novel genes as required for successful MAH infection; one encoding a probable MFS transporter and another a hypothetical protein located in immediate vicinity of six other identified virulence genes. In summary, we provide new, fundamental insights into the underlying genetic requirement of MAH for growth and host infection.\n\nAuthor summaryPulmonary disease caused by nontuberculous mycobacteria is increasing worldwide. The majority of these infections are caused by the M. avium complex (MAC), whereof >90% arise from Mycobacterium avium subsp. hominissuis (MAH). Treatment of MAH infections is currently difficult, with a combination of antibiotics given for at least 12 months. To control MAH by improved therapy, prevention and diagnostics, we need to understand the underlying mechanisms of infection. While genetic manipulation of pathogens is crucial to study pathogenesis, M. avium (Mav) has been found notoriously hard to engineer. Here, we identify an MAH strain highly susceptible to high-density transposon mutagenesis and transformation, facilitating genetic engineering and analysis of gene function. We provide crucial insights into this strains global genetic requirements for growth and infection. Surprisingly, we find that the vast majority of genes required for MAH growth and virulence (96% and 97%, respectively) have mutual orthologs in the tuberculosis-causing pathogen M. tuberculosis (Mtb). However, we also find growth and virulence genes specific to MAC species. Finally, we validate novel mycobacterial virulence factors that might serve as future drug targets for MAH-specific treatment, or translate to broader treatment of related mycobacterial diseases.

microbiology↗

bioRxiv2018

Genetic variation/evolution and differential host responses resulting from in-patient adaptation of Mycobacterium avium

Mycobacterium avium (Mav) complex (MAC) are characterized as non-tuberculosis mycobacteria and are pathogenic mainly in immunocompromised individuals. MAC strains show a wide genetic variability, and there is growing evidence suggesting that genetic differences may contribute to a varied immune response that may impact on the infection outcome. The current study aimed to characterize the genomic changes within Mav isolates collected from single patients over time and test the host immune responses to these clinical isolates. Pulsed field gel electrophoresis and whole genome sequencing was performed on 40 MAC isolates isolated from 15 patients at the Department of Medical Microbiology at St. Olavs Hospital in Trondheim, Norway. Patients (4, 9 and 13) who contributed more than two isolates were selected for further analysis. These isolates exhibited extensive sequence variation in the form of single nucleotide polymorphisms (SNPs), suggesting that Mav accumulates mutations at high rates during persistent infections. Infection of murine macrophages and mice with sequential isolates from patients showed a tendency towards increased persistence and down-regulation of inflammatory cytokines by host-adapted Mav strains. The study revealed rapid genetic evolution of Mav in chronically infected patients accompanied with change in virulence properties of the sequential mycobacterial isolates.\n\nIMPORTANCEMAC are a group of opportunistic pathogens, consisting of Mav and M. intracellulare species. Mav is found ubiquitously in the environment. In Mav infected individuals, Mav has been known to persist for long periods of time, and anti-mycobacterial drugs are unable to effectively clear the infection. The continued presence of the bacteria, could be attributed to either a single persistent strain or reinfection with the same or different strain. We examined sequential isolates collected over time from Mav infected individuals and observed that most patients carried the same strain overtime and were not re infected. We observed high rates of mutation within the serial isolates, accompanied with changes in virulence properties. In the light of increase in incidence of MAC related infections, this study highlights the possibility that host adapted Mav undergo genetic modifications to cope with the host environment and thereby persisting longer.

immunology↗