Localization in membrane microdomains of the Ig-alpha/beta component of the BCR expressed by a B lymphoma variant.
The B cell antigen receptor (BCR) composed of the ligand-binding membrane IgM (mIgM) and the signaling component, Ig-alpha/beta, is known to inducibly associate with membrane microdomains rich in cholesterol and sphingolipids, termed lipid rafts. In this study we tested whether the Ig-alpha/beta portion of the BCR has targeting information that allows it to be localized in lipid rafts. In order to do this, we cross-linked the Ig-alpha/beta on the cell surface of the variant B cell line, WEHI 303.1.5, a derivative of the immature murine B cell line WEHI 231 that lacks mu heavy chain and expresses the Ig-alpha/beta on the cell surface by itself. Using two methods to isolate detergent-insoluble, lipid raft-like fractions, we found that Ig-alpha/beta without accompanying mIgM was constitutively located in these raft-like fractions and that the amount was marginally increased after Ig-alpha/beta cross-linking. These results suggest that the Ig-alpha/beta portion of the BCR has the ability to be compartmentalized into raft-like membrane domains even when not associated with mIgM and perhaps this targeting information is normally regulated by the presence of the mIgM portion of the receptor.
Jackson
Teresa L
TL
Cell Biology Group, Department of Zoology, University of British Columbia, 6270 University Blvd, Vancouver, BC V6T 1Z4 Canada.
Santos
Lorna
L
Dang-Lawson
May
M
Matsuuchi
Linda
L
D000818:Animals; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D007136:Immunoglobulins / Q000378:metabolism*; D016393:Lymphoma, B-Cell / Q000145:classification / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism*; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*
D007136:Immunoglobulins; D011518:Proto-Oncogene Proteins; D011947:Receptors, Antigen, B-Cell; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt