Role of internalin proteins in the pathogenesis of Listeria monocytogenes

Listeria monocytogenes is a food-borne bacterium that causes gastroenteritis, meningitis, or abortion. L. monocytogenes induces its internalization (entry) into human cells and either spreads laterally in tissues or transcytoses to traverse anatomical barriers. In this review, we discuss mechanisms by which five structurally related proteins of the "internalin" family of L. monocytogenes (InlA, InlB, InlC, InlF, and InlP) interact with distinct host receptors to promote infection of human cells and/or crossing of the intestinal, blood-brain, or placental barriers. We focus on recent results demonstrating that the internalin proteins InlA, InlB, and InlC exploit exocytic pathways to stimulate transcytosis, entry, or cell-to-cell spread, respectively. We also discuss evidence that InlA-mediated transcytosis contributes to traversal of the intestinal barrier, whereas InlF promotes entry into endothelial cells to breach the blood-brain barrier. InlB also facilitates the crossing of the blood-brain barrier, but does so by extending the longevity of infected monocytes that may subsequently act as a "Trojan horse" to transfer bacteria to the brain. InlA, InlB, and InlP each contribute to fetoplacental infection by targeting syncytiotrophoblast or cytotrophoblast layers of the placenta. This work highlights the diverse functions of internalins and the complex mechanisms by which these structurally related proteins contribute to disease.

Bacterial Diversity and Population Dynamics During the Fermentation of Palm Wine From Guerrero Mexico

Palm wine is obtained by fermentation of palm tree sap. In the Pacific coast of Mexico, palm wine is called Tuba and it is consumed as a traditional fermented beverage. Tuba has empirical applications such as an auxiliary in gastrointestinal diseases and a good source of nutrients. In the present study, a next-generation sequencing of the V3-V4 regions of the 16S rRNA gene was employed to analyze bacterial diversity and population dynamics during the fermentation process of Tuba, both in laboratory controlled conditions and in commercial samples from local vendors. Taxonomic identification showed that Fructobacillus was the main genus in all the samples, following by Leuconostoc, Gluconacetobacter, Sphingomonas, and Vibrio. Alpha diversity analysis demonstrated variability between all the samples. Beta diversity clustered the bacterial population according to the collection origin of the sample. Metabolic functional profile inference showed that the members of the bacterial communities may present the vitamin, antibiotic and antioxidant biosynthesis genes. Additionally, we further investigated the correlation between the predominant genera and some composition parameters of this beverage. This study provides the basis of the bacterial community composition and functionality of the fermented beverage.

Dynamin Binding Protein Is Required for Xenopus laevis Kidney Development

The adult human kidney contains over one million nephrons, with each nephron consisting of a tube containing segments that have specialized functions in nutrient and water absorption and waste excretion. The embryonic kidney of Xenopus laevis consists of a single functional nephron composed of regions that are analogous to those found in the human nephron, making it a simple model for the study of nephrogenesis. The exocyst complex, which traffics proteins to the cell membrane in vesicles via CDC42, is essential for normal kidney development. Here, we show that the CDC42-GEF, dynamin binding protein (Dnmbp/Tuba), is essential for nephrogenesis in Xenopus. dnmbp is expressed in Xenopus embryo kidneys during development, and knockdown of Dnmbp using two separate morpholino antisense oligonucleotides results in reduced expression of late pronephric markers, whereas the expression of early markers of nephrogenesis remains unchanged. A greater reduction in expression of markers of differentiated distal and connecting tubules was seen in comparison to proximal tubule markers, indicating that Dnmbp reduction may have a greater impact on distal and connecting tubule differentiation. Additionally, Dnmbp reduction results in glomus and ciliary defects. dnmbp knockout using CRISPR results in a similar reduction of late markers of pronephric tubulogenesis and also results in edema formation in later stage embryos. Overexpression of dnmbp in the kidney also resulted in disrupted pronephric tubules, suggesting that dnmbp levels in the developing kidney are tightly regulated, with either increased or decreased levels leading to developmental defects. Together, these data suggest that Dnmbp is required for nephrogenesis.

Tricellulin regulates junctional tension of epithelial cells at tricellular contacts through Cdc42

When the surface view of each epithelial cell is compared with a polygon, its sides correspond to cell-cell junctions, whereas its vertices correspond to tricellular contacts, whose roles in epithelial cell morphogenesis have not been well studied. Here, we show that tricellulin (also known as MARVELD2), which is localized at tricellular contacts, regulates F-actin organization through Cdc42. Tricellulin-knockdown epithelial cells exhibit irregular polygonal shapes with curved cell borders and impaired organization of F-actin fibers around tricellular contacts during cell-cell junction formation. The N-terminal cytoplasmic domain of tricellulin binds to the Cdc42 guanine-nucleotide-exchange factor (GEF) Tuba (also known as DNMBP and ARHGEF36), and activates Cdc42. A tricellulin mutant that lacks the ability to bind Tuba cannot rescue the curved cell border phenotype of tricellulin-knockdown cells. These findings indicate that tricellular contacts play crucial roles in regulating the actomyosin-mediated apical junctional complex tension through the tricellulin-Tuba-Cdc42 system.

The association of serous tubal intraepithelial carcinoma with gynecologic pathologies and its role in pelvic serous cancer

OBJECTIVES

Possible primary sites of pelvic serous cancers are, fallopian tubes, ovaries or peritoneum. Recent studies have revealed that a portion of these tumors originates from serous tubal intraepithelial carcinoma (STIC) at the distal end of fallopian tubes. In this study, the association of STIC with pelvic serous carcinomas and the pathologic parameters that indicate the tubes as the primary site were assessed.

METHODS

In total, 495 pairs of fallopian tubes obtained via total abdominal hysterectomy and bilateral salpingo-oophorectomy between 2011 and 2013 were examined according to SEE-FIM protocol. Hematoxylin and eosin-stained slides were examined by pathologists. Suspicious areas were immunostained with p53 and Ki-67 to diagnose STIC precisely.

RESULTS

Of the 495 cases, 110 cases were malignant. Among 34 cases of non-uterine serous carcinomas, 13 were diagnosed with STIC. STIC was located at the fimbrial end of the fallopian tubes in 12 cases. No STIC was identified in the gynecologic malignancies other than non-uterine serous pelvic carcinomas and benign gynecologic pathologies. Comparison of the ovarian and tubal cancer cases with and without STIC did not reveal a factor that helps to define the primary site. STIC was an important factor associated in a higher portion of the cases with bilateral ovarian cancer.

CONCLUSION

The role of STIC in carcinogenesis continues to be discussed as it is unknown whether STIC is the precursor lesion or just associates with the malignancies. Discovering the accurate precursor lesions and tumor carcinogenesis is essential to prevent these malignancies and to develop early diagnostic methods.

Molecular mechanism of protrusion formation during cell-to-cell spread of Listeria

The bacterial pathogen Listeria monocytogenes spreads within human tissues using a motility process dependent on the host actin cytoskeleton. Cell-to-cell spread involves the ability of motile bacteria to remodel the host plasma membrane into protrusions, which are internalized by neighboring cells. Recent results indicate that formation of Listeria protrusions in polarized human cells involves bacterial antagonism of a host signaling pathway comprised of the scaffolding protein Tuba and its effectors N-WASP and Cdc42. These three human proteins form a complex that generates tension at apical cell junctions. Listeria relieves this tension and facilitates protrusion formation by secreting a protein called InlC. InlC interacts with a Src Homology 3 (SH3) domain in Tuba, thereby displacing N-WASP from this domain. Interaction of InlC with Tuba is needed for efficient Listeria spread in cultured human cells and infected animals. Recent structural data has elucidated the mechanistic details of InlC/Tuba interaction, revealing that InlC and N-WASP compete for partly overlapping binding surfaces in the Tuba SH3 domain. InlC binds this domain with higher affinity than N-WASP, explaining how InlC is able to disrupt Tuba/N-WASP complexes.