Toshihide Mimura

Systemic lupus erythematosus and thrombotic thrombocytopenic purpura: a case report and literature review.

AbstractWe describe a patient with systemic lupus erythematosus (SLE) who developed severe and acute thrombotic thrombocytopenic purpura (TTP). Detection of the fragmentation of peripheral red blood cells (RBC) helped the early diagnosis of TTP and the patient was rescued by extensive plasma exchange started promptly after the diagnosis. Because manifestations of TTP are similar to those in SLE, it is sometimes difficult to make an accurate diagnosis of TTP in SLE patients. We emphasise here the significance of the early diagnosis of TTP by the observation of fragmented RBC and the intensive therapy, including plasma exchange, for this very severe condition.

Integrin-mediated signal transduction in cells lacking focal adhesion kinase p125FAK.

We have previously shown that integrin‐dependent tyrosine phosphorylation of p130Cas (Cas) could be induced in a mouse fibroblast cell line that does not express focal adhesion kinase p125FAK (FAK). By analyzing FAK‐deficient (FAK−/−) cells transiently expressing Cas mutant proteins, we demonstrate here that the Src homology 3 (SH3) domain of Cas is indispensable for adhesion‐mediated Cas phosphorylation in this mutant cell line. While the FAK directly binds to Cas‐SH3, our findings imply that SH3‐binding molecule(s) other than FAK might regulate Cas phosphorylation, at least in FAK−/− cells. In this regard, we observed that FAK−/− cells expressed cell adhesion kinase β (CAKβ), a protein tyrosine kinase of the FAK subfamily. CAKβ expressed by FAK−/− cells was associated in vivo with Cas in a Cas‐SH3‐dependent manner. Moreover, integrin stimulation induces tyrosine phosphorylation of CAKβ in FAK−/− cells. Thus, our results suggest that CAKβ contributes to integrin‐mediated signal transduction in place of FAK in FAK‐deficient cells.

Protein-losing enteropathy associated with hypocomplementemia and anti-nuclear antibodies.

Abstract: We report a case of protein-losing enteropathy associated with an autoimmune disorder, presumably systemic lupus erythematosus. Although typical manifestations of systemic lupus erythematosus were lacking, a high serum cholesterol level, a low serum complement level, positivity for anti-nuclear antibody, and positivity for anti-single-strand DNA antibody suggested an autoimmune mechanism as the cause of the condition. Although immunohistological examination of duodenal and ileal biopsy specimens failed to reveal deposits of immune complex or complement in the vessels, capillary hyperpermeability was suspected as the mechanism of the condition.

Glomerular overexpression and increased tyrosine phosphorylation of focal adhesion kinase p125FAK in lupus-prone MRL/MP-lpr/lpr mice.

Much progress has been made in understanding how mammalian cells receive a diverse array of external stimuli and convert them into intracellular biochemical signals. Such efforts have identified a large number of signalling molecules. However, our knowledge is limited as to their pathophysiological role in particular diseases. We demonstrate herein that an integrin‐linked signalling molecule, focal adhesion kinase p125FAK (FAK), is overexpressed in glomeruli of lupus‐prone MRL/MP‐lpr/lpr (MRL‐lpr) mouse as compared to its congeneic MRL‐+/+ strain. Increased expression was specifically demonstrated in glomeruli but not in other tissues examined. The overexpression was observed in 16‐week‐old MRL‐lpr mice with active nephritis, as well as in younger animals at 4 weeks of age. Thus, the upregulation of FAK clearly preceded the clinical onset of nephritis. FAK in MRL‐lpr glomeruli is highly tyrosine phosphorylated and is associated with adapter protein Grb2. Previous in vitro studies have shown that the association of FAK/Grb2 links cell adhesion to the Ras pathway, which ultimately stimulates mitogen‐activated protein (MAP) kinase, an important regulator of cell proliferation. In accordance, we observed constitutive MAP kinase activation in MRL‐lpr glomeruli. Our findings suggest that signalling pathways involving FAK are activated in MRL‐lpr glomeruli, and are likely to play a role in the development and progression of autoimmune‐mediated murine nephritis.

Tyrosine phosphorylation of proteins in primary human myeloid leukemic cells stimulated by macrophage colony-stimulating factor: analysis by disease type and comparison with normal human hematopoietic cells.

We investigated tyrosine phosphorylation of proteins in primary human leukemic cells stimulated by macrophage colony-stimulating factor (M-CSF) in 60 patients with acute myeloid leukemia (AML) and 5 patients with chronic myelomonocytic leukemia and compared the findings for leukemic cells with those of normal human monocytes and bone marrow immature hematopoietic cells. M-CSF induced tyrosine phosphorylation of p140-200, p110, p60, p44, and p42 frequently, and that of p95 and p55 less frequently, in primary myeloid leukemic cells, whereas M-CSF-induced phosphorylation of proteins was not detected in the normal human hematopoietic cells tested. Of these phosphoproteins, p140-200 was phosphorylated in all patients who responded to M-CSF and was considered to be almost identical to Fms, a product of the c-fms proto-oncogene. M-CSF-induced tyrosine phosphorylation was observed frequently (89%) in AML of French-American-British class M4 and infrequently in all other subtypes of AML, including M5. In chronic myelomonocytic leukemia, M-CSF-induced protein phosphorylation was prominent in blast crisis but was not detected in the chronic phase. Both bone marrow immature cells and mature monocytes showed low responsiveness to M-CSF. These findings for responsiveness to M-CSF were correlated with the amount of Fms in each type of cell. We also identified tyrosine phosphorylation of Vav, Shc, and extracellular signal-regulated kinase by M-CSF in some cases.These findings clarified an M-CSF-specific pattern of protein tyrosine phosphorylation and the responsiveness to M-CSF of primary human myeloid cells. Particularly, enhanced phosphorylation responses to M-CSF and increased amounts of Fms protein were observed in restricted human hematopoietic cells with a premature myelomonocytic character.