Biomedical subjects

Masaru Araki

Publications and source records attributed to Masaru Araki.

3 recordsLinked to original sources

PubMed2005

A Rac switch regulates random versus directionally persistent cell migration.

Directional migration moves cells rapidly between points, whereas random migration allows cells to explore their local environments. We describe a Rac1 mechanism for determining whether cell patterns of migration are intrinsically random or directionally persistent. Rac activity promoted the formation of peripheral lamellae that mediated random migration. Decreasing Rac activity suppressed peripheral lamellae and switched the cell migration patterns of fibroblasts and epithelial cells from random to directionally persistent. In three-dimensional rather than traditional two-dimensional cell culture, cells had a lower level of Rac activity that was associated with rapid, directional migration. In contrast to the directed migration of chemotaxis, this intrinsic directional persistence of migration was not mediated by phosphatidylinositol 3'-kinase lipid signaling. Total Rac1 activity can therefore provide a regulatory switch between patterns of cell migration by a mechanism distinct from chemotaxis.

Cell Culture Techniques↗

PubMed2003

Tyrosine phosphorylation of the CrkII adaptor protein modulates cell migration.

CrkII belongs to a family of adaptor proteins that become tyrosine phosphorylated after various stimuli. We examined the role of CrkII tyrosine phosphorylation in fibronectin-induced cell migration. Overexpression of CrkII inhibited dephosphorylation of focal adhesion components such as p130 Crk-associated substrate (p130cas) and paxillin by protein tyrosine phosphatase 1B (PTP1B). Tyrosine-phosphorylated CrkII was dephosphorylated by PTP1B both in vitro and in vivo, showing for the first time that PTP1B directly dephosphorylates CrkII. A CrkII mutant in which tyrosine residue 221 was substituted by phenylalanine (CrkII-Y221F) could not be tyrosine phosphorylated, and it showed significantly increased binding to p130cas and paxillin. Enhanced binding of CrkII to p130cas has been reported to promote cell migration. Nonphosphorylated CrkII-Y221F promoted HT1080 cell migration on fibronectin, whereas wild-type CrkII did not at moderate expression levels. Moreover, co-expression of CrkII and PTP1B promoted HT1080 cell migration on fibronectin and retained tyrosine phosphorylation and binding of p130cas to CrkII, whereas paxillin tyrosine phosphorylation was reduced. These findings support the concepts that CrkII binding activity is regulated by tyrosine kinases and phosphatases, and that tyrosine phosphorylation of CrkII can downmodulate cell migration mediated by the focal adhesion kinase/p130cas pathway.

Cell Movement↗

PubMed2002

Reproduction of typical electrocardiographic findings of the Brugada syndrome using modified precordial leads.

We present a case of a patient with Brugada syndrome and aborted sudden cardiac death in whom the typical Brugada sign (coved-type ST segment elevation in the precordial leads V1 through V3) was always reproduced by the precordial leads recording on the second intercostal space even after the typical sign had disappeared. The finding indicates that recordings of precordial leads on the higher intercostal spaces are important to unmask the ST elevation in suspected patients with Brugada syndrome.

Bundle-Branch Block↗