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PubMed2026

Stratifying lung adenocarcinoma: a novel prognostic model based on mitochondrial outer membrane permeabilization activity.

UNLABELLED: Mitochondrial outer membrane permeabilization (MOMP) is a core apoptotic regulatory event that dictates mitochondrial integrity, where full activation drives cell death and sublethal dysregulation contributes to tumor genomic instability. We used the Cancer Genome Atlas lung adenocarcinoma cohort (TCGA-LUAD) as the training cohort and the Gene Expression Omnibus dataset GSE42127 as the validation cohort to identify prognostic genes related to MOMP activity in lung adenocarcinoma (LUAD) and to evaluate their potential biological significance. By intersecting MOMP-related genes with differentially expressed genes, combined with survival analysis, Mendelian randomization analysis, and 101 machine-learning algorithm combinations, seven prognostic genes, namely BIRC5, PSMD11, TNFRSF13C, YWHAZ, YWHAG, CYCS, and LTB, were identified. Next, an optimal prognostic model was constructed based on the gradient boosting machine (GBM) algorithm. Based on the risk score, LUAD patients were stratified into high- and low-risk groups, and patients in the high-risk group exhibited poorer overall survival in both the training and validation cohorts. Furthermore, a nomogram integrating the risk score and clinicopathological factors was developed and showed favorable predictive performance for 1-, 3-, and 5-year survival. Meanwhile, functional and immune analyses revealed that the high-risk group was enriched in DNA replication-related pathways and demonstrated a higher tumor mutation burden (TMB). Correlation analysis indicated that TNFRSF13C was positively correlated with activated B cells, whereas BIRC5 was negatively correlated with eosinophils, suggesting that MOMP-related genes might be involved in remodeling the immune microenvironment of LUAD. Drug sensitivity analysis showed differences in predicted half-maximal inhibitory concentration (IC50) values between the risk groups, suggesting the potential value of this model in assisting therapeutic stratification. Single-cell RNA sequencing (scRNA-seq) further identified T lymphocytes as a key cell type, with numerous prognostic genes exhibiting differential expression in T cells or dynamic changes during differentiation. We suggest that the MOMP-related signature established in this study may provide a reference for prognostic stratification in LUAD and offers candidate prognostic genes for subsequent experimental and clinical validation. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at https://doi.org/10.1007/s13205-026-05058-6.

Lung adenocarcinoma↗

PubMed1991

Isolation and partial characterization of a 39 kDa major outer membrane protein of Actinobacillus actinomycetemcomitans Y4.

The outer membrane fractions of Actinobacillus actinomycetemcomitans, which were extracted from whole cells with cetyl trimethyl ammonium bromide and CaCl2, contained four major outer membrane proteins (MOMP) of 39, 37, 36 and 30 kDa. The 39 kDa MOMP of A. actinomycetemcomitans was sequentially purified by extraction with Zwittergent 3-14 detergent, anion-exchange chromatography and gel filtration chromatography. Analysis of amino acid composition and N-terminal amino acid sequence of 20 residues of purified 39 kDa MOMP was performed. Although some of the periodontitis patient sera reacted strongly with 39 kDa and 30 kDa MOMP in crude outer membrane fractions, purified 39 kDa MOMP showed decreased immunoreactivity with the human sera.

Actinobacillus↗

PubMed1990

Expression of the Chlamydia trachomatis major outer membrane protein-encoding gene in Escherichia coli: role of the 3' end in mRNA stability.

The major outer membrane protein (MOMP)-encoding gene (omp1) of Chlamydia trachomatis has been cloned into Escherichia coli and partially sequenced. This recombinant gene expresses a full-length 40-kDa product, which is recognized by a monoclonal antibody directed against the species-specific epitope of MOMP. The recombinant omp1 is expressed in either insertion orientation, indicating that it utilizes its own promoter system. The endogenous omp1 promoter possesses a relatively low activity despite the high level of MOMP expression. Deletion of a 520-bp fragment at the 3' end encoding 39 amino acids (aa) at the C terminus and the remainder of the noncoding region leads to a significant decrease in mRNA stability and loss of protein synthesis. When the MOMP-encoding plasmid was introduced into E. coli minicells, it expressed 40- and 43-kDa proteins; however, inhibition of post-translational processing by ethanol revealed only a 43-kDa protein. These data indicate that the unprocessed omp1 gene product contains a 22-aa leader sequence which is cleaved during translocation to the outer membrane, to yield a processed 40-kDa protein. The recombinant MOMP was localized to the outer membrane E. coli fraction, comparable to the location of the native C. trachomatis protein.

Amino Acid Sequence↗

PubMed1994

Monoclonal antibody to a major outer membrane protein of feline Chlamydia psittaci: antibody specificity and anti-idiotype antibody production.

A murine monoclonal antibody, F1-8, was developed against the purified major outer membrane protein (MOMP) of Chlamydia psittaci feline pneumonitis (FPn). F1-8 showed a serotype-specific activity against intact Fpn elementary bodies in a micro-immunofluorescence assay. In immunoblot, F1-8 reacted only with the Fpn MOMP but did not react with the MOMPs from other strains of C. psittaci and C. trachomatis. F1-8 neutralized Fpn infectivity in L929 cell culture in a dose-dependent and complement independent fashion. These results suggested that the monoclonal antibody (mAb) binds with an epitope on the MOMP region that is exposed at the cell surface and plays an important role in FPn infection. Polyclonal anti-idiotype (anti-Id) antibodies to mAb F1-8 were elicited by F1-8 coupled to keyhole limpet hemocyanin. These anti-Id antibodies inhibited F1-8 binding to FPn MOMP.

Animals↗

PubMed2005

Mitochondrial fusion and fission in the control of apoptosis.

Mitochondrial outer membrane permeabilization (MOMP) determines the point-of-no-return of most if not all signal-transduction cascades leading to cell death. It has been postulated that the molecular mechanism leading to MOMP could depend on the activation of the mitochondrial fission machinery mediated by proteins from the dynamin superfamily. However, recent work suggests that, depending on the specific apoptosis induction pathway, mitochondrial fission can occur independently or downstream from MOMP. Moreover, fragmentation of the mitochondrial network can inhibit MOMP and apoptosis in response to a particular range of lethal stimuli, namely those relying on Ca(2+) waves. Failure to transmit the Ca(2+) wave through disconnected mitochondria then interrupts the propagation of the pro-apoptotic signal. Thus, mitochondrial fission can either enhance or reduce the probability of MOMP and consequent cell death, depending on the initial lethal stimulus.

Apoptosis↗

PubMed2005

Protection of turkeys against Chlamydophila psittaci challenge by DNA and rMOMP vaccination and evaluation of the immunomodulating effect of 1 alpha,25-dihydroxyvitamin D(3).

Plasmid DNA expressing the major outer membrane protein (MOMP) of an avian Chlamydophila psittaci serovar D strain and recombinant MOMP (rMOMP) with or without the immunomodulating adjuvant 1 alpha,25-dihydroxyvitamin D(3) have been tested for their ability to elicit an immune response and induce protection in turkeys against challenge with the same serovar. Three vaccination strategies were compared: priming and boosting with either pcDNA1::MOMP or rMOMP and priming with pcDNA1::MOMP followed by rMOMP boosting. Turkeys primed with pcDNA1::MOMP showed significant protection against Cp. psittaci challenge, turkeys primed with rMOMP did not. The steroid hormone 1 alpha,25-dihydroxyvitamin D(3) augmented serum and mucosal antibody titres. However, higher antibody titres were not related to better protection and even had a negative effect on especially bacterial excretion.

Adjuvants, Immunologic↗

PubMed2003

Immunization with the Chlamydia trachomatis major outer membrane protein, using the outer surface protein A of Borrelia burgdorferi as an adjuvant, can induce protection against a chlamydial genital challenge.

Two strains of mice C3H/HeN (H-2(k)) and BALB/c (H-2(d)) were immunized with the Chlamydia trachomatis mouse pneumonitis (MoPn) major outer membrane protein (MOMP) using the Borrelia burgdorferi outer surface protein A (OspA) as an adjuvant. As a control, groups of mice were inoculated with ovalbumin instead of MOMP. Female mice were immunized using three different routes: intramuscular (i.m.) plus subcutaneous (s.c.), intranasal (i.n.) and perivaginal and perisacral (p.vag.+p.sac.). Significant humoral and cell mediated immune responses developed particularly in mice inoculated by the i.m.+s.c. routes as determined by the levels of chlamydial specific antibody in the serum and genital secretions and a T-cell proliferative assay. Following immunization the animals were challenged in the genital tract with C. trachomatis MoPn and the course of the infection followed by vaginal cultures. Significant protection against infection was achieved in the C3H/HeN mice inoculated i.m.+s.c. with MOMP+OspA, as shown by the intensity and duration of vaginal cultures, and by the number of mice with positive cultures. On the other hand in BALB/c mice there was only a decrease in the number of animals with positive vaginal cultures. Six weeks after the challenge the mice were mated and the outcome of the pregnancy evaluated. In both the C3H/HeN and the BALB/c mice immunized i.m.+s.c. with MOMP+OspA there was significant protection against infertility as shown by the number of animals with bilateral fertility and number of embryos per uterine horn. In conclusion, immunization using C. trachomatis MOMP, and B. burgdorferi OspA as an adjuvant, can induce significant protection against a chlamydial genital challenge.

Adjuvants, Immunologic↗

PubMed1999

Vaccination of mice with DNA plasmids coding for the Chlamydia trachomatis major outer membrane protein elicits an immune response but fails to protect against a genital challenge.

A DNA plasmid encoding the gene of the major outer membrane protein (MOMP) of the Chlamydia trachomatis mouse pneumonitis (MoPn) serovar and three plasmids containing the variable domains (VD) of the MOMP were constructed. Female mice were inoculated with the plasmids and 60 days later were challenged in the genital tract with C. trachomatis. Six weeks after challenge female mice were caged with male mice and the course of the mating followed. Mice immunized with the MOMP plasmids mounted weak humoral and cell mediated immune responses. However, following the genital challenge no significant differences in vaginal shedding were observed between the groups immunized with the MOMP and control plasmids. In addition, the fertility rates were similar in the experimental and negative control groups. In conclusion, vaccination with DNA plasmids encoding the MOMP elicited a modest immune response but did not protect against infection or disease.

Animals↗

PubMedDate not supplied

Antigenic structure of surface-exposed regions of the major outer-membrane protein of Chlamydia trachomatis.

The major outer-membrane protein (MOMP) of Chlamydia trachomatis displays a number of surface-exposed epitopes. Some of these are shared by all or some of the 15 known serovars, whereas others are serovar-specific. With use of epitope-mapping analysis of limited proteolytic digests of purified MOMPs with monoclonal antibodies, the present study assessed whether the same or different surface-exposed regions of the protein express these different epitopes. Results with both chymotrypsin and the staphylococcal V8 protease for MOMP of serovar F indicated that many of the shared surface epitopes are clustered in one region whereas the serovar-reactive epitope is located in a separate region. Analysis of MOMPs from all the serovars with a species-specific monoclonal antibody indicated that each MOMP possesses a structurally analogous region that expresses this epitope. Such a region might play a role in pathogenic mechanisms that are shared by all serovars.

Antibodies, Monoclonal↗

PubMed1995

Sequence conservation in the major outer membrane protein gene among Chlamydia trachomatis strains isolated from the upper and lower urogenital tract.

To determine the extent of nucleotide sequence variation in the major outer membrane protein (MOMP) gene among 27 clinical isolates of Chlamydia trachomatis, the MOMP gene was amplified from 13 strains isolated from the endometrium of patients with pelvic inflammatory disease and high titers of anti-chlamydial antibodies and from 14 strains isolated from the cervix of patients with presumed first-time chlamydial infection. Amplified MOMP variable domain DNA from these isolates was directly sequenced and compared with previously published results. Very little sequence heterogeneity in the MOMP variable domains was found in all 27 clinical isolates, suggesting that MOMP sequence heterogeneity is not often associated with the spread of C. trachomatis to the upper genital tract and is not common in the chlamydial strains in the patient population studied.

Amino Acid Sequence↗

PubMed1991

Restriction pattern of the major outer-membrane protein gene provides evidence for a homogeneous invasive group among ruminant isolates of Chlamydia psittaci.

Thirty-six ruminant isolates of Chlamydia psittaci, previously classified as invasive or non-invasive in a mouse model of virulence, were compared by analysing AluI restriction patterns of the major outer-membrane protein (MOMP) gene after DNA amplification by the polymerase chain reaction. The 24 invasive isolates, although from various origins, all belonged to serotype 1 and represented a strictly homogeneous group sharing a specific MOMP-gene restriction pattern that was not observed in the non-invasive strains. On the other hand, the 12 non-invasive strains, although all belonging to serotype 2, constituted a heterogeneous group with eight distinct MOMP-gene restriction patterns. However, all eight patterns shared a 180 bp fragment or the corresponding restricted fragments of 110 and 70 bp. MOMP-gene restriction patterns also clearly distinguished the ruminant strains from an avian C. psittaci isolate, a C. pneumoniae isolate and two C. trachomatis isolates which were studied for comparison. The homogeneous character of the invasive C. psittaci strains argues strongly for their genetic relatedness. Our results illustrate the usefulness of the MOMP-gene restriction mapping in typing chlamydiae.

Animals↗

PubMed1991

Nucleotide sequence and taxonomic value of the major outer membrane protein gene of Chlamydia pneumoniae IOL-207.

Chlamydia pneumoniae IOL-207 genomic DNA was hybridized with a 1.5 kb labelled DNA probe containing the 3' region of the coding sequence for the major outer membrane protein (MOMP) of C. trachomatis serovar L1. An 8.5 kb Bg/II fragment containing the complete MOMP gene was cloned into lambda EMBL3. Two hybridizing EcoRI fragments were sub-cloned into the lambda ZAP II cloning vector and the resulting plasmids were used as templates for sequencing both strands of the C. pneumoniae MOMP gene. Computer taxonomic studies using the nucleotide and inferred amino acid sequence of the MOMP of C. pneumoniae IOL-207 and all known chlamydial MOMP sequences supported the designation of C. pneumoniae as a new species, but electron microscope studies suggested that the presence of pear-shaped elementary bodies (EBs) may not be a reliable taxonomic criterion.

Amino Acid Sequence↗

PubMed1986

Outer membrane proteins from Legionella pneumophila serogroups and other Legionella species.

Outer membranes were isolated from eight serogroups of L. pneumophila and five other Legionella species. The protein composition of the membranes was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A single, disulfide stabilized protein with a molecular size of 29,000 to 30,000 daltons was found to be the major outer membrane protein (MOMP) of all the serogroups. The equivalent of the L. pneumophila MOMP was not observed in any of the other Legionella species examined. Silver staining of sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels revealed distinctive patterns for each serogroup and other Legionella species that were not observed by staining with Coomassie blue and may result from the presence of lipopolysaccharide in the membrane preparations. The MOMP from serogroup 1 was isolated by exposing crude peptidoglycan to detergent in the presence of heat and reducing agent and was found to be tightly associated with lipopolysaccharide. Antibodies to this complex were used to probe the outer membranes of the remaining, L. pneumophila serogroups and other Legionella species by Western blotting. Serogroup 1 anti-MOMP antibodies were found to react with the MOMP from the remaining seven serogroups examined, whereas antibodies directed against the lipopolysaccharide of serogroup 1 only reacted with lipopolysaccharide from two of the remaining seven serogroups.

Bacterial Outer Membrane Proteins↗

PubMed1988

Differential effect of trypsin on infectivity of Chlamydia trachomatis: loss of infectivity requires cleavage of major outer membrane protein variable domains II and IV.

The initial interaction of chlamydiae with host cells is not well understood. Chlamydial cell surface components that function in attachment are key virulence factors, and their identification is critical for understanding the pathogenic strategies of this very successful parasite. We used trypsin proteolysis of chlamydiae to define surface components that function in chlamydia-host cell interactions. We found that trypsin had a differential effect on the infectivity of Chlamydia trachomatis serovars B and L2 for HeLa 229 cells. Trypsin treatment resulted in a significant loss of attachment and infectivity of serovar B but had no effect on the infectivity of serovar L2. Fluorograms of chlamydiae metabolically labeled with 14C-amino acids and treated with trypsin showed that the major outer membrane protein (MOMP) of both serovars was cleaved. Evidence for two trypsin cleavage sites was found for the serovar B MOMP. One cleavage site was located between lysine 145 and valine 146 in variable domain (VD) II of the protein. The second site was located between lysine 309 and threonine 310 in VD IV. In contrast, the serovar L2 MOMP was cleaved only at lysine 309 in VD IV. These results suggest a functional role for MOMP in chlamydial attachment and implicate VDs II and IV of MOMP in this interaction.

Amino Acid Sequence↗

PubMed1991

Cloning and sequence analysis of the major outer membrane protein gene of Chlamydia psittaci 6BC.

The gene encoding the major outer membrane protein (MOMP) of the psittacine Chlamydia psittaci strain 6BC was cloned and sequenced. N-terminal protein sequencing of the mature MOMP indicated that it is posttranslationally processed at a site identical to the site previously identified in the MOMP of Chlamydia trachomatis L2. The nucleotide sequence of the C. psittaci 6BC MOMP gene was found to be 67 to 68% identical to those of human C. trachomatis strains, 73% identical to that of Chlamydia pneumoniae IOL-207, 79% identical to that of the C. psittaci guinea pig inclusion conjunctivitis strain, GPIC, and 83% identical to that of the C. psittaci ovine abortion strain S26/3. In contrast, the 6BC sequence was found to be greater than 99% identical to the sequences reported for two strains of C. psittaci, A22/M and Cal-10 meningopneumonitis, believed to be of nonpsittacine avian origin. Monoclonal antibody analysis confirmed the nonpsittacine avian origin of A22/M but identified the Cal-10 strain from which the MOMP gene was previously sequenced as a psittacine strain. These results confirm that psittacine and nonpsittacine avian strains of C. psittaci are closely related and distinct from the mammalian guinea pig inclusion conjunctivitis and ovine abortion strains of C. psittaci.

Amino Acid Sequence↗

PubMed1994

Binding of the glycan of the major outer membrane protein of Chlamydia trachomatis to HeLa cells.

Recent studies have shown that the major outer membrane protein (MOMP) of Chlamydia trachomatis is glycosylated. The glycan of the MOMP of C. trachomatis serovar L2 was separated from the glycoprotein with N-glycanase, reduced with tritiated NaBH4, and tested for its ability to interact with HeLa cells. The [3H]glycan was shown to attach readily to HeLa cells at 25 or 37 degrees C. This process was slower at 4 degrees C. Competition for possibly similar receptor sites on HeLa cells between the glycan and a sugar, an aminosaccharide, or elementary bodies (EBs) was then studied. D-Galactose, D-mannose, or N-acetylglucosamine was shown to reduce the attachment of the glycan to HeLa cells at concentrations of 0.1 to 0.5 M. Sedoheptulose, D-fructose, or sialic acid did not inhibit the binding of glycan to HeLa cells. The presence of at least 100 native or UV-inactivated EBs per HeLa cell interfered with the glycan's ability to bind to HeLa cells. Heat-inactivated EBs did not compete with the glycan for binding. In the reverse situation, nonradiolabeled glycan prevented the EBs from infecting and forming inclusions in HeLa cells. Incubation of [3H]glycan with rabbit immune serum prepared against antigens of whole EB and the MOMP inhibited attachment. In contrast, incubation of glycan with mouse monoclonal antibodies against the protein portion of the MOMP or the chlamydial lipopolysaccharide did not inhibit attachment. These results suggest that the glycan portion of the MOMP is involved in the attachment process of C. trachomatis organisms to HeLa cells.

Bacterial Adhesion↗

PubMed1996

Fine mapping of outer membrane protein P2 antigenic sites which vary during persistent infection by Haemophilus influenzae.

Antigenic drift of the major outer membrane protein (MOMP) P2 of nonencapsulated Haemophilus influenzae as observed during persistent infections in patients with chronic bronchitis was mimicked in a rabbit model in which H. influenzae persisted in subcutaneous cages. The antigenic drift resulted from amino acid substitutions in potentially surface-exposed loops of MOMP P2. Since in a rabbit model the appearance of antigenic variants was associated with the presence of strain-specific bactericidal antibodies (L. Vogel, B. Duim, F. Geluk, P. Eijk, H. Jansen, J. Dankert, and L. van Alphen, Infect. Immun. 64:980-986, 1996), we determined the epitope specificities of these bactericidal antibodies. The eight loops of MOMP P2 of H. influenzae d1 were separately expressed as fusion proteins with glutathione S-transferase. Sera of rabbits persistently infected with H. influenzae reacted with the loop 5 and loop 6 fusion proteins in immunoblotting and enzyme-linked immunosorbent assay. For fine mapping of the epitopes with pepscan analysis, overlapping synthetic peptides consisting of 12 amino acids were made. Rabbit sera contained antibodies reacting with peptides derived from loop 5 and peptides containing amino acids of the side of loop 6. In addition, MOMP P2 variant-specific reactions with the amino acids located at the tip of loop 6 were detected. The rabbit sera showed variant-specific complement-dependent bactericidal activities, which were eliminated by affinity chromatography with fusion proteins of loop 6 but not of loop 5. We conclude that, during persistence of H. influenzae in rabbits, variant-specific bactericidal antibodies are elicited to the variable tip of MOMP P2 loop 6.

Animals↗

PubMed1996

The major outer membrane protein of a single Chlamydia trachomatis serovar can possess more than one serovar-specific epitope.

The major outer membrane proteins (MOMPs) of human Chlamydia trachomatis serovars exhibit four regions of variable amino acid sequences (VS1 to VS4) harboring serovar-specific B-cell epitopes. Antibody responses to these epitopes may contribute to acquired protection against human chlamydial infection. MOMP B-cell epitopes defined by 22 different serovar-specific or bispecific murine monoclonal antibodies were localized with synthetic peptides representing the four VS regions of seven genital serovars (D, Da, E, F, G, H, and K). Serovar F possessed two distinct serovar-specific epitopes, located in VS2 and VS4, while serovar K possessed three distinct serovar-specific epitopes, located in VS1, VS2, and VS4. Serovar D- and serovar Da-specific epitopes were located in VS1. Regardless of whether the serovar was from the B (serovars D, Da, and E), C (serovars H and K), or F-G (serovars F and G) serogroup, all serovar-specific epitopes were found in three discrete subgroups of MOMPs. These subregions comprised all central portion of VS1, residues 70 to 77; the amino-terminal half of VS2, residues 139 to 149; and the carboxyl-terminal third of VS4, residues 305 to 315. Monoclonal antibodies to each of these subregions neutralized infectivity in standard HaK cell culture assays. These findings are relevant to the development of an MOMP or MOMP subunit vaccine.

Amino Acid Sequence↗