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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Role of membrane microdomains in PTH-mediated down-regulation of NaPi-IIa in opossum kidney cells.

BACKGROUND: Parathyroid hormone ( PTH) rapidly down-regulates type IIa sodium-dependent phosphate transporter (NaPi-IIa) via an endocytic pathway. Since the relationship between PTH signaling and NaPi-IIa endocytosis has not been explored, we investigated the role of membrane microdomains in this process. METHODS: We examined the submembrane localization of NaPi-IIa in opossum kidney (OK-N2) cells that stably expressed human NaPi-IIa, and searched for a PTH- induced specific phosphorylating substrate on their membrane microdomains by immunoblotting with specific antibody against phospho substrates of protein kinases. RESULTS: We found that NaPi-IIa was primarily localized in low-density membrane (LDM) domains of the plasma membrane; PTH reduced the levels of immunoreactive NaPi-IIa in these domains. Furthermore, PTH activated both protein kinase A (PKA) and protein kinase Calpha (PKCa) and increased the phosphorylation of 250 kD and 80 kD substrates; this latter substrate was identified as ezrin, which a member of the ezrin-radixin-moesin (ERM) protein family. In response to PTH, ezrin was phosphorylated by both PKA and PKC. Dominant negative ezrin blocked the reduction in NaPi-IIa expression in the LDM domains that was induced by PTH. CONCLUSION: These data suggest that NaPi-IIa and PTH- induced phosphorylated proteins that include ezrin are compartmentalized in LDM microdomains. This compartmentalization may play an important role in the down-regulation of NaPi-IIa via endocytosis.[1]


  1. Role of membrane microdomains in PTH-mediated down-regulation of NaPi-IIa in opossum kidney cells. Nashiki, K., Taketani, Y., Takeichi, T., Sawada, N., Yamamoto, H., Ichikawa, M., Arai, H., Miyamoto, K., Takeda, E. Kidney Int. (2005) [Pubmed]
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