Down‐regulation of FXYD3 protein, a regulator of Na+,K+‐ATPase, in human colorectal cancers

• Published in: The FASEB journal 2007-04, Vol.21 (5), p.A535-A535
• Main Authors: Asano, Shinji, Sakai, Hideki, Tsukada, Kazuhiro, Yamamoto, Hiroto, Okumura, Kenzo
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.21.5.A535

The FXYD family proteins are small proteins which contain a single transmembrane domain, and the □gFXYD (Phe‐Xaa‐Tyr‐Asp) motif□h in the ectodomain. They associate with the Na+,K+‐ATPase to modulate its function. Among seven members of the FXYD proteins, the FXYD3 (Mat‐8) associates with the Na+,K+‐ATPase and decreases its affinity for Na+ and K+. The FXYD3 was also reported to be involved in cell proliferation and tumorigenesis. Here, we studied the mRNA expression level of FXYD3 in human cultured cell lines, and normal tissues by the real‐time PCR, and found that the mRNA was highly expressed in a breast cancer cell line, MCF‐7 and a pancreatic cancer cell line, T3M‐4. The mRNA expression level of FXYD3 was highest in colons. We also studied the protein expression of FXYD3 by using a monoclonal antibody against human FXYD3. The FXYD3 protein with a molecular mass of 13 kDa was also highly expressed in human colon. It is interesting that the FXYD3 protein was down‐regulated in human colorectal cancers compared with the surrounding normal mucosae. This down‐regulation of the FXYD3 seems to correspond with the down‐regulation of Na+,K+‐ATPase α1‐subunit in the same colorectal cancers.