Detergent-resistant microdomains offer no refuge for proteins phosphorylated by the IgE receptor.
When the high affinity receptor for IgE and related receptors become aggregated, they emigrate to specialized microdomains of the plasma membrane that are enriched in certain lipids and lipid-anchored proteins. Among the latter are the kinases that initiate signaling cascade(s) by phosphorylating the receptors. In studying the IgE receptor, we explored whether, in addition to their potential role in enhancing the initiation of signaling by the kinase(s), the microdomains might augment the stimulation by excluding phosphatases. In vitro assessment of phosphatase activity, using either a relevant or irrelevant substrate, suggested that the microdomains were deficient in phosphatase activity, but, in vivo, proteins confined to the microdomains were found to be no less vulnerable to dephosphorylation than those outside such domains. In the course of our experiments, we observed that the procedures routinely used to isolate the detergent-resistant domains dissociated the receptor for IgE, thereby artificially accentuating the observed preferential distribution of phosphorylated subunits in the microdomains.
Peirce
M
M
Section on Chemical Immunology, Arthritis and Rheumatism Branch, NIAMS, National Institutes of Health, Bethesda, Maryland 20892-1820, USA.
Metzger
H
H
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism; D002458:Cell Fractionation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D021962:Membrane Microdomains / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D017830:Octoxynol / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017455:Receptors, IgE / Q000378:metabolism*; D013347:Subcellular Fractions; D013395:Sucrose / Q000378:metabolism; D013997:Time Factors; D019061:src-Family Kinases / Q000737:chemistry / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D003902:Detergents; D047908:Intracellular Signaling Peptides and Proteins; C110810:LAT protein, human; C491734:Lat protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; D017455:Receptors, IgE; D013395:Sucrose; D017830:Octoxynol; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D010744:Phosphoric Monoester Hydrolases; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C516727:Ptpn11 protein, rat; C509248:Ptpn6 protein, mouse; C509250:Ptpn6 protein, rat