LIM domain-containing adaptor, leupaxin, localizes in focal adhesion and suppresses the integrin-induced tyrosine phosphorylation of paxillin.

Focal adhesion (FA) consists of multiple cellular proteins including paxillin and serves as a center for adhesion-mediated signaling. The assembly and disassembly of FAs is regulated by locally produced intracellular signals, and tyrosine phosphorylation of paxillin has been implicated in this process. A Lin-11 Isl-1 Mec-3 (LIM) domain-containing adaptor protein, leupaxin, a member of the paxillin family, is expressed in leukocytes as well as in certain cancer cells, and shares overall structural characteristics with paxillin. However, it remains unknown whether leupaxin and paxillin cooperate with or antagonize each other in integrin signaling. Here we show that leupaxin potently represses the tyrosine phosphorylation of paxillin. When expressed in mouse thymoma BW5147 cells bound to ICAM-1, leupaxin accumulated in FA-like patches in the cell periphery. When expressed in NIH3T3 and HEK293T cells, leupaxin localized to FAs upon cell adhesion to fibronectin and strongly suppressed the integrin-induced tyrosine phosphorylation of paxillin. In integrin-stimulated HEK293T cells, leupaxin's LIM3 domain appeared essential for selective FA localization and the suppression of paxillin tyrosine phosphorylation. Leupaxin's LD3 motif, which is critical for stable association with FAK, was dispensable for leupaxin's suppressive ability. In addition, leupaxin reduced the spreading of NIH3T3 cells on fibronectin, which required both the LD3 motif and LIM3 domain. When expressed in human leukocytic K562 cells, leupaxin significantly suppressed integrin alpha5beta1-mediated cell adhesion to fibronectin and the tyrosine phosphorylation of paxillin. These findings indicate that leupaxin functions as a paxillin counterpart that potently suppresses the tyrosine phosphorylation of paxillin during integrin signaling.

The expression of anamorsin in diffuse large B cell lymphoma: possible prognostic biomarker for low IPI patients.

Anamorsin is a cell-death-defying factor, which was originally isolated as a molecule that conferred resistance to apoptosis induced by growth factor starvation. In order to evaluate anamorsin expression levels in malignant lymphoma, we immunostained paraffin-embedded sections with anti-anamorsin monoclonal antibodies. About 40% (89/234) of sections from patients with diffuse large B cell lymphoma (DLBCL) showed strong anamorsin expression. Comparing the level of anamorsin expression in DLBCL patients with their clinical features (i.e., overall survival rate, International Prognostic Index (IPI) parameters, and treatment response) revealed no significant correlation between anamorsin expression levels and these clinical features. However, anamorsin expression in DLBCL patients with a low IPI was shown to be an unfavorable biomarker, especially in the patients who received chemotherapy without rituximab. It is suggested that anamorsin might play some roles in the abnormal growth of DLBCL.

[Hypersensitivity reactions to multiple drugs during the course of hairy cell leukemia treated with 2-chlorodeoxyadenosine].

A 38-year-man developed diffuse erythema 3 days after the administration of 2-chlorodeoxyadenosine (cladribine or 2-CdA) and many other drugs for hairy cell leukemia (HCL). Patch-testing and scratch patch-testing showed positive reactions for clindamycin (10%, 30%) at 24 hours and 48 hours. Furthermore, provocation-testing showed positive reactions for sulfamethoxazole.trimethoprim, allopurinol, fluconazole, so our diagnosis was erythroderma-type drug eruption due to clindamycin, sulfamethoxazole-trimethoprim, allopurinol, fluconazole. Cutaneous side-effects associated with cladribine have seldom been described in cases of HCL. Our case suggests that there is a relationship between the drug hypersensitivity and the prolonged suppressed CD4 cell levels caused by cladribine.

Lymphocyte binding to MAdCAM-1 via alpha4beta7 integrin activates a signal transduction pathway involving tyrosine phosphorylation of paxillin and p105(Cas-L).

Alpha4beta7 integrin mediates lymphocyte trafficking to mucosal lymphoid organs by interacting with the mucosal vascular addressin MAdCAM-1. While the structural basis for the alpha4beta7 integrin-MAdCAM-1 interaction has been well characterized, less is known about the signal transduction pathways that regulate the alpha4beta7 integrin-mediated lymphocyte interaction with MAdCAM-1-expressing endothelial cells. Here we demonstrate that ligation of alpha4beta7 integrin with MAdCAM-1 induces a prominent tyrosine phosphorylation of paxillin and a 105-kDa protein (p105) that is reactive with an anti-p130(Cas) antibody, in the mouse T-cell line TK-1. Cloning and expression of a full-length cDNA encoding the mouse p105(Cas-L) revealed that the p105 molecule is a mouse ortholog of p105(Cas-L). We also demonstrated that crosslinking of alpha4beta7 integrin with MAdCAM-1 induces the rapid tyrosine phosphorylation of paxillin and p105(Cas-L) in normal lymphocytes and that PMA stimulation enhances the tyrosine phosphorylation of p105(Cas-L) but not of paxillin. These results suggest that intracellular signals initiated by alpha4beta7 integrin involve the tyrosine phosphorylation of paxillin and p105(Cas-L), which are differentially regulated, at least in part, by mechanisms that are PMA-sensitive or -insensitive.