Hsp90 recognizes a common surface on client kinases.

Hsp90 is a highly abundant chaperone whose clientele includes hundreds of cellular proteins, many of which are central players in key signal transduction pathways and the majority of which are protein kinases. In light of the variety of Hsp90 clientele, the mechanism of selectivity of the chaperone toward its client proteins is a major open question. Focusing on human kinases, we have demonstrated that the chaperone recognizes a common surface in the amino-terminal lobe of kinases from diverse families, including two newly identified clients, NFkappaB-inducing kinase and death-associated protein kinase, and the oncoprotein HER2/ErbB-2.

Hsp90 restrains ErbB-2/HER2 signalling by limiting heterodimer formation.

ErbB-2/HER2 is an oncogenic tyrosine kinase that regulates a signalling network by forming ligand-induced heterodimers with several growth factor receptors of the ErbB family. Hsp90 and co-chaperones regulate degradation of ErbB-2 but not other ErbB members. Here, we report that the role of Hsp90 in modulating the ErbB network extends beyond regulation of protein stability.

Tolerance induction by veto CTLs in the TCR transgenic 2C mouse model. II. Deletion of effector cells by Fas-Fas ligand apoptosis.

The direct assay of veto CTLs in the 2C mouse model enables monitoring, by FACS, the fate of the TCR transgenic effector CD8(+) T cells, the transgene of which can be stained with clonotypic Ab 1B2. After the addition of veto cells, CD8(+)1B2(+) effector cells increasingly express annexin V, and maximal apoptosis is attained 72 h after initiation of MLR. This veto activity can be partially blocked by anti-CD8 Abs directed against the allele expressed by the veto CTLs, but not by the effector cells.

Tolerance induction by veto CTLs in the TCR transgenic 2C mouse model. I. Relative reactivity of different veto cells.

Several bone marrow cells and lymphocyte subpopulations, known as veto cells, were shown to induce transplantation tolerance across major histocompatibility Ags. Due to the low frequency of the effector T cells against which the veto cells inhibitory activity is aimed, the fate of the effector cells was traditionally followed indirectly by functional limiting dilution assays, which are cumbersome and depend on numerous parameters. In the present study the fate of the effector T cells was monitored directly by FACS, using TCR transgenic mouse CD8(+) T cells in which the transgene is directed against H-2(d) (the 2C model).

Eradication of B-CLL by autologous and allogeneic host nonreactive anti-third-party CTLs.

Establishment of cell lines capable of killing leukemia cells, in the absence of alloreactivity against normal host cells, represents a most desirable goal in bone marrow transplantation (BMT) and cancer immunotherapy. By using a human --> mouse chimeric model, we demonstrate that allogeneic anti-third-party cytotoxic T lymphocytes (CTLs) depleted of alloreactivity are endowed with a potent anti-B-cell chronic lymphocytic leukemia (B-CLL) reactivity. Likewise, CTL preparations generated from autologous T cells of the same patients with B-CLL exhibited comparable leukemia eradication, suggesting that the reactivity of allogeneic anti-third-party CTLs is not mediated by residual antihost clones.