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D D Kaplan

Publications and source records attributed to D D Kaplan.

4 recordsLinked to original sources
PubMed2001

Distinct regions of the cadherin cytoplasmic domain are essential for functional interaction with Galpha 12 and beta-catenin.

Heterotrimeric G proteins of the G(12) subfamily mediate cellular signals leading to events such as cytoskeletal rearrangements, cell proliferation, and oncogenic transformation. Several recent studies have revealed direct effector proteins through which G(12) subfamily members may transmit signals leading to various cellular responses. Our laboratory recently demonstrated that Galpha(12) and Galpha(13) specifically interact with the cytoplasmic domains of several members of the cadherin family of cell adhesion molecules (Meigs, T. E., Fields, T. A., McKee, D. D., and Casey, P. J. (2001) Proc. Natl. Acad. Sci. U. S. A. 98, 519-524). This interaction causes beta-catenin to release from cadherin and relocalize to the cytoplasm and nucleus, where it participates in transcriptional activation. Here we report that two distinct regions of the epithelial cadherin (E-cadherin) tail are required for interaction with beta-catenin and Galpha(12), respectively. Deletion of an acidic, 19-amino acid region of E-cadherin abolishes its ability to bind beta-catenin in vitro, to inhibit beta-catenin-mediated transactivation, or to stabilize beta-catenin; causes subcellular mislocalization of beta-catenin; and disrupts cadherin-mediated cell adhesion. On the other hand, deletion of a distinct 11-amino acid region of E-cadherin dramatically attenuates interaction with Galpha(12); furthermore, Galpha(12) is ineffective in stimulating beta-catenin release from an E-cadherin cytoplasmic domain lacking this putative Galpha(12)-binding region. These findings indicate that Galpha(12) and beta-catenin do not compete for the same binding site on cadherin and provide molecular targets for selectively disrupting the interaction of these proteins with cadherin.

Animals↗
PubMed1999

Rho and Rho kinase mediate thrombin-stimulated vascular smooth muscle cell DNA synthesis and migration.

Aberrant regulation of smooth muscle cell proliferation and migration is associated with the pathophysiology of vascular disorders such as hypertension, atherosclerosis, restenosis, and graft rejection. To elucidate molecular mechanisms that regulate proliferation and migration of vascular smooth muscle cells, we determined whether signaling through the small G protein Rho is involved in thrombin- and phenylephrine-stimulated proliferation and migration of rat aortic smooth muscle cells (RASMCs). Thrombin and the thrombin peptide SFLLRNP stimulated DNA synthesis of RASMCs as measured by [3H]thymidine incorporation. Both ligands also increased cell migration as measured by the Boyden chamber method. L-Phenylephrine failed to induce either of these responses but increased inositol phosphate accumulation and mitogen-activated protein kinase activation in these cells, which indicated that the cells were responsive to alpha1-adrenergic stimulation. The C3 exoenzyme, which ADP-ribosylates and inactivates Rho, fully inhibited both thrombin-stimulated proliferation and migration but had no effect on inositol phosphate accumulation. In addition, Y-27632, an inhibitor of the Rho effector p160ROCK/Rho kinase, decreased thrombin-stimulated DNA synthesis and migration. To directly examine Rho activation, Rho-[35S]GTPgammaS binding was measured. The addition of the thrombin peptide SFLLRNP, but not phenylephrine, to RASMC lysates resulted in a significant increase in Rho-[35S]GTPgammaS binding. Thrombin and SFLLRNP, but not phenylephrine, also increased membrane-associated Rho in intact RASMCs, consistent with selective activation of Rho by thrombin. These results indicate that thrombin activates Rho in RASMCs and establish Rho as a critical mediator of thrombin receptor effects on DNA synthesis and cell migration in these cells.

Adenosine Diphosphate Ribose↗
PubMed1997

Estimating residence times and their associated errors in patient absorbed-dose calculation.

OBJECTIVE: An approach for estimating organ residence times (tau) and their errors in patient internal emitter radiation dosage calculations has been determined. METHODS: Using a modeling algorithm and its associated parameters, chimeric anti-CEA monoclonal antibody (cT84.66) patient organ uptake data and residence times of source organ activity were calculated. Through the covariance matrix of the model's parameters and subsequent Monte Carlo simulations, errors in organ residence time (gamma tau) also were estimated RESULTS: These relative tau errors were found to be model-dependent; increasing as the number of organs being simultaneously modeled in a set of two patients being considered for 90Y-cT84.66 radioimmunotherapy. CONCLUSION: Use of modeling and Monte Carlo methods provide a general, direct procedure for calculating the degree of accuracy of activity integrals and other mathematical functions of kinetic variables.

Algorithms↗