Biomedical subjects

Lisa Drake

Publications and source records attributed to Lisa Drake.

3 recordsLinked to original sources

PubMed2006

BCR ubiquitination controls BCR-mediated antigen processing and presentation.

BCR-mediated antigen processing occurs at immunologically relevant antigen concentrations and hinges on the trafficking of antigen-BCR (Ag-BCR) complexes to class II-containing multivesicular bodies (MVBs) termed MIICs. However, the molecular mechanism underlying the trafficking of Ag-BCR complexes to and within MIICs is not well understood. In contrast, the trafficking of the epidermal growth factor receptor (EGFR) to and within MVBs occurs via a well-characterized ubiquitin-dependent mechanism, which is blocked by acute inhibition of proteasome activity. Using a highly characterized antigen-specific model system, it was determined that the immunoglobulin heavy chain subunit of the IgM BCR of normal (ie, nontransformed) B cells is ubiquitinated. Moreover, acute inhibition of proteasome activity delays the formation of ubiquitinated ligand-BCR complexes, alters the intracellular trafficking of internalized Ag-BCR complexes, and selectively blocks the BCR-mediated processing and presentation of cognate antigen, without inhibiting the endocytosis, processing, and presentation of non-cognate antigen internalized by fluidphase endocytosis. These results demonstrate that the trafficking of Ag-BCR complexes to and within MVB-like antigen processing compartments occurs via a molecular mechanism with similarities to that used by the EGFR, and establishes the EGFR as a paradigm for the further analysis of Ag-BCR trafficking to and within MIICs.

Animals↗

PubMed2006

Functional and structural requirements for the internalization of distinct BCR-ligand complexes.

Antigen (Ag) binding to the BCR rapidly initiates two important events: a phosphorylation cascade that results in the production of secondary signaling intermediaries and the internalization of Ag-BCR complexes. Previous studies using anti-BCR antibodies (Ab) have suggested that BCR signaling is an essential requirement for BCR endocytosis and have further implicated lipid rafts as essential platforms for both BCR functions. However, published data from our laboratory indicate that lipid rafts and consequently raft-mediated signaling are dispensable for BCR-mediated internalization of Ag-specific BCR. Therefore, we investigated the relationship between BCR signaling and endocytosis by defining the role of early kinase signaling in the BCR-mediated internalization of a model Ag (haptenated protein). The results demonstrate that Src kinases and Syk-mediated BCR signaling are not essential for BCR-mediated Ag internalization. Moreover, by comparing Ag and Ab, it was determined that while both localize to clathrin-coated pits, the internalization of Ab-BCR complexes is more susceptible to inhibition of signaling and highly sensitive to disruption of lipid rafts and the actin cytoskeleton compared to Ag-BCR complexes. Thus, these results demonstrate that the nature of the ligand ultimately determines the functional requirements and relative contribution of lipid rafts and other membrane structures to the internalization of BCR-ligand complexes.

Animals↗

PubMed2006

Doxorubicin and dexamethasone followed by thalidomide and dexamethasone is an effective well tolerated initial therapy for multiple myeloma.

Among the drug combinations designed for the initial treatment of multiple myeloma, none has been unequivocally shown to be superior. However, a regimen leading to a high response rate and a low incidence of adverse events is highly desirable. We report the results of a phase II clinical trial involving 45 patients with Durie-Salmon stage II and III multiple myeloma. Doxorubicin and dexamethasone were given for 2 or 3 months followed by thalidomide and dexamethasone for 2 months (AD-TD regimen) with prophylactic antibiotics and daily aspirin (81 mg/d). Among the 42 patients whose response could be assessed, 38 responded to therapy (90.5%). The intent-to-treat response rate was 84.4% with seven complete responses (CR 15.5%), nine near complete responses (nCR 20.0%), and 22 partial responses (PR 48.9%). Two patients had stable disease (4.4%), and two progression of disease (4.4%). Normalization of the free light chain ratio after one or two cycles of treatment was highly predictive of achievement of CR or nCR. Patients tolerated the treatment well although five patients developed thromboembolic complications (11%). AD-TD administered with low dose aspirin for deep vein thrombosis prophylaxis was well tolerated and yielded a high response rate with minimal treatment-related morbidity.

Adult↗