Lipid phosphate phosphatases 1 and 3 are localized in distinct lipid rafts.
Lipid phosphate phosphatases (LPPs), integral membrane proteins with six transmembrane domains, dephosphorylate a variety of extracellular lipid phosphates. Although LPP3 is already known to bind to Triton X-100-insoluble rafts, we here report that LPP1 is also associated with lipid rafts distinct from those harboring LPP3. We found that LPP1 was Triton X-100-soluble, but CHAPS-insoluble in LNCaP cells endogenously expressing LPP1 and several LPP1 cDNA-transfected cells including NIH3T3 fibroblasts. In addition to the non-ionic detergent insolubility, LPP1 further possessed several properties formulated for raft-localizing proteins as follows: first, the CHAPS-insolubility was resistant to the actin-disrupting drug cytochalasin D; second, the CHAPS-insoluble LPP1 floated in an Optiprep density gradient; third, the CHAPS insolubility of LPP1 was lost by cholesterol depletion; and finally, the subcellular distribution pattern of LPP1 exclusively overlapped with that of a raft marker, cholera toxin B subunit. Interestingly, confocal microscopic analysis showed that LPP1 was distributed to membrane compartments distinct from those of LPP3. Analysis using various LPP1/LPP3 chimeras revealed that their first extracellular regions determine the different Triton X-100 solubilities. These results indicate that LPP1 and LPP3 are distributed in distinct lipid rafts that may provide unique microenvironments defining their non-redundant physiological functions.
Kai
Masahiro
M
Department of Biochemistry, Sapporo Medical University School of Medicine, West-17, South-1, Sapporo 060-8556.
Sakane
Fumio
F
Jia
Yan-Jun
YJ
Imai
Shin-Ichi
S
Yasuda
Satoshi
S
Kanoh
Hideo
H
D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D002793:Cholic Acids / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D021962:Membrane Microdomains / Q000201:enzymology*; D051379:Mice; D018613:Microscopy, Confocal; D041681:NIH 3T3 Cells; D017830:Octoxynol / Q000494:pharmacology; D010711:Phosphatidate Phosphatase / Q000378:metabolism*; D012995:Solubility
D002793:Cholic Acids; D007527:Isoenzymes; D015638:Cytochalasin D; D017830:Octoxynol; C112948:lipid phosphate phosphatase; D010711:Phosphatidate Phosphatase; C479566:Plpp3 protein, mouse; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate