IKK-related kinases are key regulators of innate immunity and oncogenesis. While their effects on transcription are well characterized, their cytoplasmic functions remain poorly understood. Drosophila IKK-related kinase, IKKɛ, regulates cytoskeletal organization and cell elongation. Here, we demonstrate that IKKɛ is activated locally at the tip of growing mechanosensory bristles and regulates the rapid shuttling of recycling endosomes, independent of its roles in F-actin organization and caspase signaling. IKKɛ regulates the localization of recycling endosome regulators Rab11 and Dynein and phosphorylates their adaptor molecule, Nuclear fallout (Nuf). Nuf's negative regulation by IKKɛ suggests that local activation of IKKɛ inhibits Dynein on incoming recycling endosomes, converting them for outward transport. Mammalian IKK-related kinases also regulate the recycling endosomes' distribution by phosphorylating the Nuf homolog Rab11-FIP3. Our results establish an evolutionarily conserved function of IKK-related kinases in regulating recycling endosome dynamics and point to a key role of endosome dynamics in cell morphogenesis.
Afadin interacts with the cytoplasmic region of nectins, which are immunoglobulin-like cell adhesion molecules at adherens junctions, and links them to the actin cytoskeleton. Afadin regulates activities of cells in culture such as directional motility, proliferation and survival. We used Cre-loxP technology to generate mice conditionally lacking afadin specifically in the intestinal epithelia after birth. The loss of afadin caused increased paracellular permeability in the intestinal mucosa and enhanced susceptibility to the tissue destruction induced by dextran sulfate sodium. The junctional architecture of the intestinal epithelia appeared to be preserved, whereas the deficiency of afadin caused the mislocalization of nectin-2 and nectin-3 from adherens junctions to basolateral membrane domains but not that of other components of apical junctions. By contrast, such phenotypic changes were undetected in mice lacking nectin-2, nectin-3 or both. These findings suggest that afadin plays crucial roles, independently of the role as the nectin–afadin module, in barrier function and homeostasis of the intestinal epithelia once the epithelial structure has been established.
The fine-tuning of BMP signals is critical for many aspects of complex organogenesis. In this report, we show that the augmentation of BMP signaling by a BMP-binding secreted factor, Crossveinless2 (Cv2), is essential for the early embryonic development of mammalian nephrons. In the Cv2-null mouse, the number of cap condensates (clusters of nephron progenitors, which normally express Cv2) was decreased, and the condensate cells exhibited a reduced level of aggregation. In these Cv2(-/-) condensates, the level of phosphorylated Smad1 (pSmad1) was substantially lowered. The loss of a Bmp7 allele in the Cv2(-/-) mouse enhanced the cap condensate defects and further decreased the level of pSmad1 in this tissue. These observations indicated that Cv2 has a pro-BMP function in early nephrogenesis. Interestingly, the renal defects of the Cv2(-/-) mutant were totally suppressed by a null mutation of Twisted gastrulation (Tsg), which encodes another BMP-binding factor, showing that Cv2 exerts its pro-BMP nephrogenic function Tsg-dependently. By using an embryonic kidney cell line, we presented experimental evidence showing that Cv2 enhances pro-BMP activity of Tsg. These findings revealed the molecular hierarchy between extracellular modifiers that orchestrate local BMP signal peaks in the organogenetic microenvironment.
ABSTRACT. To clarify the relationship between M cells and intestinal microflora, histoplanimetrical investigation into the bacterial colonization and the differentiation to M cells was carried out in rat Peyer's patch under physiological conditions. The follicle-associated epithelium (FAE), except for the narrow area of apical region, was closely covered with both neighboring intestinal villi and a thick mucous layer, the latter of which also filled the intervillous spaces as well as the space between the FAE and the neighboring intestinal villi. Indigenous bacteria adhered almost constantly to the narrow areas of apical regions of both intestinal villi and the FAE. Bacterial colonies were occasionally located on the basal to middle region of FAE, where M cells also appeared, forming large pockets. When bacterial colonies were located on the basal to middle region of FAE, bacteria with the same morphological characteristics also proliferated in the intervillous spaces neighboring the Peyer's patch. In cases with no bacterial colonies on the basal to middle region of FAE, however, M cells were rare in the FAE. Histoplanimetrical analysis showed the similar distribution pattern of bacterial colonies on the FAE and M cells in the FAE. M cells ultrastructurally engulfed indigenous bacteria, which were then transported to the pockets. These results suggest that indigenous bacterial colonization on the FAE stimulates the differentiation of M cells in the FAE under physiological conditions. The uptake of bacteria by M cells might contribute the regulation of the development of indigenous bacterial colonies in the small intestine.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.