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J Wienands

Publications and source records attributed to J Wienands.

7 recordsLinked to original sources
PubMed1992

Glycosyl-phosphatidylinositol linkage as a mechanism for cell-surface expression of immunoglobulin D.

The B-cell antigen receptor of the IgM and IgD class is a multimeric complex consisting of the membrane-bound form of the immunoglobulin molecule and two other proteins, Ig-alpha and Ig-beta. The Ig-alpha and Ig-beta proteins form a disulphide-linked alpha/beta heterodimer and are encoded by the mb-1 (ref 9, 10) and B29 genes, respectively. Surface expression of the membrane-bound IgM molecule requires assembly with the alpha/beta heterodimer. The IgD molecule, however, can be expressed on the cell surface in an alpha/beta-dependent and -independent form. We show here that in the alpha/beta-independent form the IgD molecule is anchored in the plasma membrane through a glycosyl-phosphatidylinositol linker. In the presence of the alpha/beta heterodimer, most of the otherwise glycosyl-phosphatidylinositol-linked IgD molecule is expressed on the cell surface as transmembrane proteins.

Biological Transport↗
PubMed1991

The B cell antigen receptor of class IgD can be expressed on the cell surface in two different forms.

Membrane-bound immunoglobulins of the IgM and IgD class are expressed on the B cell surface in association with a disulfide-linked heterodimer consisting of alpha and beta subunits. While the alpha component of the IgM antigen receptor (IgM-alpha, 34 kDa) is encoded by the B cell-specific gene mb-1, the gene coding for IgD-alpha (35 kDa) has not yet been identified. We show here that the alpha component of the IgD antigen receptor is also encoded by the mb-1 gene. The difference in molecular weight between IgM-alpha and IgD-alpha thus seems to be due to post-translational modifications of the mb-1 gene product. We also demonstrate that the previously described myeloma variant J558L delta m2.6 expresses an alternative form of the IgD antigen receptor, which does not contain an alpha/beta heterodimer.

Animals↗
PubMed1990

Membrane IgM and IgD molecules fail to transduce Ca2+ mobilizing signals when expressed on differentiated B lineage cells.

We have measured Ca2+ mobilization in a panel of B lineage cell lines after stimulation with anti-Ig to assess whether membrane Ig transduces a functional signal in cells that are representative of immature, mature, or terminally differentiated stages. For these studies, three transfected cell lines which express the same IgM molecule (300-19 microns lambda 36/8, K46-17 microns lambda, and J558L microns lambda 3) as well as two lines expressing an identical IgD molecule (K46 delta m2.6 and J558L delta m8.8) were used. Cross-linking of membrane Ig on IgM+ or IgD+ lymphomas (K46-17 microns lambda or K46 delta m2.6) resulted in a Ca2+ mobilization response that is similar to that seen in mature, resting B cells. Both intracellular release and extracellular influx of Ca2+ were observed. In contrast, ligation of membrane Ig on an IgM+ pre-B cell line (300 - 19 microns lambda 36/8) induced extracellular influx of Ca2+ but no detectable intracellular release. Finally, cross-linking of membrane Ig on IgM+ or IgD+ plasmacytomas (J558L microns 3 or J558L delta m8.8) or an IgD+ B cell hybridoma (B1.8.delta 1) expressing an endogenous Ig gene, did not result in a detectable Ca2+ mobilization response. Importantly, stimulation of cells with the GTP-binding protein activator, aluminum fluoride, resulted in a comparable Ca2+ mobilization response in all cell lines. In view of the fact that aluminum fluoride induced a Ca2+ response in the terminally differentiated B cell lines, J558L microns 3, J558L delta m8.8, and B1.8.delta 1, it is likely that there is an alteration in the signal transduction cascade at some point proximal to GTP binding protein activation. This finding suggests that differentiation of the B cell is accompanied by the loss or alteration of one or more components that couple membrane Ig to subsequent signal transduction elements. Finally, it has previously been demonstrated that the IgM+ cell lines described above, express the recently described membrane Ig-associated protein, B34. Thus, it is apparent based on the fact that the J558L microns 3 cell line does not mobilize Ca2+ after stimulation with anti-Ig, that coexpression of B34 in association with membrane Ig does not constitute a functional receptor complex capable of activating GTP-binding proteins that in turn regulate Ca2+ mobilization.

Aluminum↗
PubMed1990

Molecular components of the B cell antigen receptor complex of class IgD differ partly from those of IgM.

Two classes of immunoglobulin, IgM and IgD, are present as antigen receptors on the surface of mature B lymphocytes. We show here that IgD molecules are noncovalently associated in the B cell membrane with a heterodimer consisting of two proteins of 35 kd (IgD-alpha) and 39 kd (Ig-beta), respectively. The two novel proteins are not found in the IgD-expressing myeloma J558L delta m, which fails to bring IgD antigen receptor onto the cell surface. In a surface IgD positive variant line of this myeloma, however, membrane-bound IgD molecules are associated with the heterodimer, suggesting that the formation of an antigen receptor complex is required for surface IgD expression. We further demonstrate that the IgD-associated heterodimer differs partly from that of the IgM antigen receptor and that its binding to the heavy chain only requires the presence of the last constant domain and the transmembrane part of the delta m chain.

Animals↗