Article

Transepithelial Projections from Basal Cells Are Luminal Sensors in Pseudostratified Epithelia

Center for Systems Biology, Program in Membrane Biology/Nephrology Division, Massachusetts General Hospital, Boston, MA 02114, USA.
Cell (Impact Factor: 31.96). 01/2009; 135(6):1108-17. DOI: 10.1016/j.cell.2008.10.020
Source: PubMed

ABSTRACT Basal cells are by definition located on the basolateral side of several epithelia, and they have never been observed reaching the lumen. Using high-resolution 3D confocal imaging, we report that basal cells extend long and slender cytoplasmic projections that not only reach toward the lumen but can cross the tight junction barrier in some epithelia of the male reproductive and respiratory tracts. In this way, the basal cell plasma membrane is exposed to the luminal environment. In the epididymis, in which luminal acidification is crucial for sperm maturation and storage, these projections contain the angiotensin II type 2 receptor (AGTR2). Activation of AGTR2 by luminal angiotensin II, increases proton secretion by adjacent clear cells, which are devoid of AGTR2. We propose a paradigm in which basal cells scan and sense the luminal environment of pseudostratified epithelia and modulate epithelial function by a mechanism involving crosstalk with other epithelial cells.

0 Bookmarks
 · 
145 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: When the surface view of each epithelial cell is compared with a polygon, its sides correspond to cell-cell junctions, while its vertices correspond to tricellular contacts, whose roles in epithelial cell morphogenesis have not been well studied. Here, we show that tricellulin, which is localized at tricellular contacts, regulates F-actin organization via 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 a Cdc42 guanine nucleotide exchange factor, Tuba, and activates Cdc42. A tricellulin mutant that lacks the ability of Tuba binding 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.
    Journal of Cell Science 08/2014; 127(19). DOI:10.1242/jcs.150607 · 5.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Basal cells play a critical role in the response of the airway epithelium to injury and are recently recognized to also contribute to epithelial immunity. Antimicrobial proteins and peptides are essential effector molecules in this airway epithelial innate immunity. However, little is known about the specific role of basal cells in antimicrobial protein and peptide production and about the regulation of the ubiquitous antimicrobial protein RNase 7. In this study, we report that basal cells are the principal cell type producing RNase 7 in cultured primary bronchial epithelial cells (PBEC). Exposure of submerged cultured PBEC (primarily consisting of basal cells) to the respiratory pathogen nontypeable Haemophilus influenzae resulted in a marked increase in expression of RNase 7, although this was not observed in differentiated air-liquid interface cultured PBEC. However, transient epithelial injury in air-liquid interface-cultured PBEC induced by cigarette smoke exposure led to epidermal growth factor receptor-mediated expression of RNase 7 in remaining basal cells. The selective induction of RNase 7 in basal cells by cigarette smoke was demonstrated using confocal microscopy and by examining isolated luminal and basal cell fractions. Taken together, these findings demonstrate a phenotype-specific innate immune activity of airway epithelial basal cells, which serves as a second line of airway epithelial defense that is induced by airway epithelial injury. Copyright © 2015 by The American Association of Immunologists, Inc.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The epithelium lining the epididymis in the male reproductive tract maintains a luminal environment that promotes sperm cell maturation. This process is dependent on the coordinated expression of many genes that encode proteins with a role in epithelial transport. We previously generated genome-wide maps of open chromatin in primary human epididymis epithelial (HEE) cells to identify potential regulatory elements controlling coordinated gene expression in the epididymis epithelium. Subsequent in-silico analysis identified transcription factor binding sites (TFBS) that were over-represented in the HEE open chromatin, include the motif for paired box 2 (PAX2). PAX2 is a critical transcriptional regulator of urogenital tract development, which has been well studied in the kidney but is unexplored in the epididymis. Due to the limited lifespan of primary HEE cells in culture, we investigated the role of PAX2 in an immortalized HEE cell line (REP). First, REP cells were evaluated by DNase-seq and the PAX2-binding motif was again identified as an overrepresented TFBS within intergenic open chromatin, though on fewer chromosomes than in the primary HEE cells. To identify PAX2-target genes in REP cells, RNA-seq analysis was performed after siRNA-mediated depletion of PAX2 and compared to that with a non-targeting siRNA. In response to PAX2-represssion, 3135 transcripts were differentially expressed (1333 up-regulated and 1802 down-regulated). Novel PAX2 targets included multiple genes encoding proteins with predicted functions in the epididymis epithelium.
    Molecular Human Reproduction 09/2014; 20(12). DOI:10.1093/molehr/gau075 · 3.48 Impact Factor