| First Author | Asghar MN | Year | 2016 |
| Journal | Am J Physiol Gastrointest Liver Physiol | Volume | 310 |
| Issue | 11 | Pages | G1147-54 |
| PubMed ID | 27125276 | Mgi Jnum | J:319239 |
| Mgi Id | MGI:6863301 | Doi | 10.1152/ajpgi.00354.2015 |
| Citation | Asghar MN, et al. (2016) Keratin 8 knockdown leads to loss of the chloride transporter DRA in the colon. Am J Physiol Gastrointest Liver Physiol 310(11):G1147-54 |
| abstractText | Keratins (K) are intermediate filament proteins important in protection from stress. The roles of keratins in the intestine are not clear, but K8 knockout (K8(-/-)) mice develop a Th2-type colonic inflammation, epithelial hyperproliferation, and mild diarrhea caused by a keratin level-dependent decrease in short-circuit current and net sodium and chloride absorption in the distal colon. The lack of K8 leads to mistargeting or altered levels of membrane proteins in colonocytes; however, the main transporter responsible for the keratin-related ion transport defect is unknown. We here analyzed protein and mRNA levels of candidate ion transporters CFTR, PAT-1, NHE-3, and DRA in ileum, cecum, and proximal and distal colon. Although no differences were observed for CFTR, PAT-1, or NHE-3, DRA mRNA levels were decreased by three- to fourfold and DRA protein was almost entirely lost in K8(-/-) cecum and proximal and distal colon compared with K8(+/+), whereas the levels in ileum were normal. In K8(+/-) mice, DRA mRNA levels were unaltered, while decreased DRA protein levels were detected in the proximal colon. Immunofluorescence staining confirmed the loss of DRA in K8(-/-) distal colon, while K8(+/-) displayed a similar but more patchy apical DRA distribution compared with K8(+/+) DRA was similarly decreased when K8 was knocked down in Caco-2 cells, confirming that K8 levels modulate DRA levels in an inflammation-independent manner. Taken together, the loss of DRA in the K8(-/-) mouse colon and cecum explains the dramatic chloride transport defect and diarrheal phenotype after K8 inactivation and identifies K8 as a novel regulator of DRA. |
