RGD Reference Report - Partitioning of NaPi cotransporter in cholesterol-, sphingomyelin-, and glycosphingolipid-enriched membrane domains modulates NaPi protein diffusion, clustering, and activity. - Rat Genome Database

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Partitioning of NaPi cotransporter in cholesterol-, sphingomyelin-, and glycosphingolipid-enriched membrane domains modulates NaPi protein diffusion, clustering, and activity.

Authors: Inoue, M  Digman, MA  Cheng, M  Breusegem, SY  Halaihel, N  Sorribas, V  Mantulin, WW  Gratton, E  Barry, NP  Levi, M 
Citation: Inoue M, etal., J Biol Chem. 2004 Nov 19;279(47):49160-71. Epub 2004 Sep 7.
RGD ID: 7243096
Pubmed: PMID:15355967   (View Abstract at PubMed)
DOI: DOI:10.1074/jbc.M408942200   (Journal Full-text)

In dietary potassium deficiency there is a decrease in the transport activity of the type IIa sodium/phosphate cotransporter protein (NaPi) despite an increase in its apical membrane abundance. This novel posttranslational regulation of NaPi activity is mediated by the increased glycosphingolipid content of the potassium-deficient apical membrane. However, the mechanisms by which these lipids modulate NaPi activity have not been determined. We determined if in potassium deficiency NaPi is increasingly partitioned in cholesterol-, sphingomyelin-, and glycosphingolipid-enriched microdomains of the apical membrane and if the increased presence of NaPi in these microdomains modulates its activity. By using a detergent-free density gradient flotation technique, we found that 80% of the apical membrane NaPi partitions into the low density cholesterol-, sphingomyelin-, and GM1-enriched fractions characterized as "lipid raft" fractions. In potassium deficiency, a higher proportion of NaPi was localized in the lipid raft fractions. By combining fluorescence correlation spectroscopy and photon counting histogram methods for control and potassium-deficient apical membranes reconstituted into giant unilamellar vesicles, we showed a 2-fold decrease in lateral diffusion of NaPi protein and a greater than 2-fold increase in size of protein aggregates/clusters in potassium deficiency. Our results indicate that NaPi protein is localized in membrane microdomains, that in potassium deficiency a larger proportion of NaPi protein is present in these microdomains, and that NaPi lateral diffusion is slowed down and NaPi aggregation/clustering is increased in potassium deficiency, both of which could be associated with the decreased Na/Pi cotransport activity in potassium deficiency.



RGD Manual Disease Annotations    Click to see Annotation Detail View
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
SLC34A1HumanPotassium Deficiency  ISOSlc34a1 (Rattus norvegicus)protein:decreased expression:renal cortex and brush border membrane (rat)RGD 
Slc34a1RatPotassium Deficiency  IEP protein:decreased expression:renal cortex and brush border membrane (rat)RGD 
Slc34a1MousePotassium Deficiency  ISOSlc34a1 (Rattus norvegicus)protein:decreased expression:renal cortex and brush border membrane (rat)RGD 

Objects Annotated

Genes (Rattus norvegicus)
Slc34a1  (solute carrier family 34 member 1)

Genes (Mus musculus)
Slc34a1  (solute carrier family 34 (sodium phosphate), member 1)

Genes (Homo sapiens)
SLC34A1  (solute carrier family 34 member 1)


Additional Information