Contribution of the LIM domain and nebulin-repeats to the interaction of Lasp-2 with actin filaments and focal adhesions.

Lasp-2 binds to actin filaments and concentrates in the actin bundles of filopodia and lamellipodia in neural cells and focal adhesions in fibroblastic cells. Lasp-2 has three structural regions: a LIM domain, a nebulin-repeat region, and an SH3 domain; however, the region(s) responsible for its interactions with actin filaments and focal adhesions are still unclear. In this study, we revealed that the N-terminal fragment from the LIM domain to the first nebulin-repeat module (LIM-n1) retained actin-binding activity and showed a similar subcellular localization to full-length lasp-2 in neural cells.

Identification of EphB6 variant-derived epitope peptides recognized by cytotoxic T-lymphocytes from HLA-A24+ malignant glioma patients.

We found previously that EphB6, a member of the erythropoietin-producing hepatocyte (Eph) receptor tyrosine kinase family, was preferentially expressed in malignant gliomas. In the present study, RT-PCR revealed a putative secretory variant form of human EphB6 that was expressed in the majority of glioma cell lines, though not in normal tissues. The variant has a unique 54 amino acid sequence that is not found in the normal EphB6.

Differences in the regulation of microtubule stability by the pro-rich region variants of microtubule-associated protein 4.

We have recently reported a neural variant of microtubule-associated protein 4 with a short pro-rich region (MAP4-SP). Here, we show that the neural MAP4 has reduced microtubule-stabilizing activity, compared to the ubiquitous MAP4 with a long pro-rich region (MAP4-LP), both in vitro and in vivo. Fluorescence recovery after photobleaching analyses revealed that the interaction of MAP4-SP with the microtubules is very rapid, with a half-time of fluorescence recovery of 7 +/- 2.

Short-term retention of actin filament binding proteins on lamellipodial actin bundles.

Actin filaments are organised into sub-compartments of meshwork and bundles in lamellipodia. Localisation of fascin, the LIM and SH3 domain protein 1 (lasp-1), and lasp-2 to the bundles suggest their involvement in that organisation; however, their contributions remain unclear. We have compared the turnover of these proteins with actin at the bundle.

Ferritin forms dynamic oligomers to associate with microtubules in vivo: implication for the role of microtubules in iron metabolism.

Ferritin, a ubiquitously distributed iron storage protein, has been reported to interact with microtubules in vitro (Hasan et al., 2005, FEBS journal 272:822-831). Here, we demonstrate that ferritin binds with the microtubules in an oligomeric form and that the microtubule-bound ferritin contains more than two-fold amount of iron compared to the unbound ferritin fraction in vitro.

The pre-mRNA-splicing factor SF3a66 functions as a microtubule-binding and -bundling protein.

SF3a (splicing factor 3a) complex is an essential component of U2 snRNPs (small nuclear ribonucleoprotein particles), which are involved in pre-mRNA splicing. This complex consists of three subunits: SF3a60, SF3a66 and SF3a120. Here, we report a possible non-canonical function of a well-characterized RNA-splicing factor, SF3a66.

A novel LIM and SH3 protein (lasp-2) highly expressing in chicken brain.

From eluates of F-actin affinity chromatography of chicken brain, we identified a novel actin-binding protein (lasp-2) whose gene was predicted in silico. We cloned cDNA of chicken lasp-2 and analyzed its structure, expression, activity, and localization with lasp-1 (LIM and SH3 protein 1), a previously identified actin-binding protein closely related to lasp-2. Chicken lasp-2 showed high homology to mammalian putative lasp-2.

IRSp53 is colocalised with WAVE2 at the tips of protruding lamellipodia and filopodia independently of Mena.

The insulin receptor tyrosine kinase substrate p53 (IRSp53) links Rac and WAVE2 and has been implicated in lamellipodia protrusion. Recently, however, IRSp53 has been reported to bind to both Cdc42 and Mena to induce filopodia. To shed independent light on IRSp53 function we determined the localisations and dynamics of IRSp53 and WAVE2 in B16 melanoma cells.

Differential localization of WAVE isoforms in filopodia and lamellipodia of the neuronal growth cone.

The formation and extension of filopodia in response to an extracellular stimulus by guidance cues determine the path of growth cone advance. Actin-filament bundling and actin polymerization at the tips supply the driving force behind the formation and elongation. We tried to clarify how signals in response to extracellular cues are transformed to induce filopodial generation and extension.

WICH, a novel verprolin homology domain-containing protein that functions cooperatively with N-WASP in actin-microspike formation.

We describe a novel protein that contains a verprolin-homology (V) region, through which several actin-regulating proteins, including Wiskott-Aldrich syndrome protein (WASP) family members, bind directly to actin. The amino acid sequence is homologous to the sequences of WASP-interacting protein (WIP) and CR16, both of which associate with WASP and/or N-WASP, and thus these three proteins constitute a new protein family. We named the protein WICH (WIP- and CR16-homologous protein).