Editors' ChoiceEpithelia

Luminal Sensors from the Basal Side

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Science Signaling  16 Dec 2008:
Vol. 1, Issue 50, pp. ec428
DOI: 10.1126/scisignal.150ec428

Shum et al. used cell-specific labeling, confocal microscopy, and three-dimensional reconstruction to show that, in several pseudostratified epithelia, basal cells extend projections that go between the epithelial cells and are in contact with the lumen. This phenomenon was observed in epididymis (both rat and human), rat coagulating gland (similar to the prostate), and rat trachea. Detailed analysis of the rat epididymis revealed that the frequency of these projections varied, with less than 10% of basal cells exhibiting this trait in proximal vas deferens and about 60% extending luminal projections in more distal regions. The morphology of these projections varied, with some appearing just beneath tight junctions and some passing through tight junctions at which three epithelial cells met. The renin-angiotensin system regulates male fertility. Shum et al. detected angiotensin II type 2 (AGTR2) receptors only in the basal cells, not in the clear cells on the luminal side that are responsible for proton pumping that acidifies the lumen to keep sperm dormant during maturation and storage. Perfusion of rat epididymides with angiotensin II (AngII) triggered the extension of proton pump-enriched microvilli from the clear cells and stimulated proton secretion. Addition of an AGTR2, but not an AGTR1, antagonist blocked these effects of AngII on clear cells. Nitric oxide (NO) is produced in response to activation of AGTR2, and application of a NO donor also stimulated extension of the proton pump-enriched microvilli, whereas pharmacological inhibition of NO production or of the NO target soluble guanylate cyclase blocked the clear cell response. Thus, the authors suggest that the luminal projections of the basal cells serve as sensors of luminal hormones and transmit signals to neighboring cells to regulate their activity and function.

W. W. C. Shum, N. Da Silva, M. McKee, P. J. S. Smith, D. Brown, S. Breton, Transepithelial projections from basal cells are luminal sensors in pseudostratified epithelia. Cell 135, 1108–1117 (2008). [Online Journal]