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Yuko Mimori-Kiyosue

Publications and source records attributed to Yuko Mimori-Kiyosue.

6 recordsLinked to original sources
PubMed2006

CLASPs attach microtubule plus ends to the cell cortex through a complex with LL5beta.

CLASPs are mammalian microtubule-stabilizing proteins that can mediate the interaction between distal microtubule ends and the cell cortex. Using mass spectrometry-based assays, we have identified two CLASP partners, LL5beta and ELKS. LL5beta and ELKS form a complex that colocalizes with CLASPs at the cortex of HeLa cells as well as at the leading edge of motile fibroblasts. LL5beta is required for cortical CLASP accumulation and microtubule stabilization in HeLa cells, while ELKS plays an accessory role in these processes. LL5beta is a phosphatidylinositol-3,4,5-triphosphate (PIP3) binding protein, and its recruitment to the cell cortex is influenced by PI3 kinase activity but does not require intact microtubules. Cortical clusters of LL5beta and ELKS do not overlap with focal adhesions but often form in their vicinity and can affect their size. We propose that LL5beta and ELKS can form a PIP3-regulated cortical platform to which CLASPs attach distal microtubule ends.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Mammalian CLASPs are required for mitotic spindle organization and kinetochore alignment.

CLASP1 and CLASP2 are homologous mammalian proteins, which associate with the ends of growing microtubules, as well as the cell cortex and the kinetochores of mitotic chromosomes. Previous studies have shown that in interphase cells CLASPs can attach microtubule plus ends to the cortex and stabilize them by repeatedly rescuing them from depolymerization. Here we show that CLASP1 and 2 play similar and redundant roles in organizing the mitotic apparatus in HeLa cells. Simultaneous depletion of both CLASPs causes mitotic spindle defects and a significant metaphase delay, which often results in abnormal exit from mitosis. Metaphase delay is associated with decreased kinetochore tension, increased kinetochore oscillations and more rapid microtubule growth. We show that the association of CLASP2 with the kinetochores relies on its C-terminal domain, but is independent of microtubules or association with CLIP-170. We propose that CLASPs exhibit at the kinetochores an activity similar to that at the cortex, providing apparent stabilization of microtubules by locally reducing the amplitude of growth/shortening episodes at the microtubule ends. This local stabilization of microtubules is essential for the formation of normal metaphase spindle, completion of anaphase and cytokinesis.

Animals↗
PubMed2005

CLASP1 and CLASP2 bind to EB1 and regulate microtubule plus-end dynamics at the cell cortex.

CLIP-associating protein (CLASP) 1 and CLASP2 are mammalian microtubule (MT) plus-end binding proteins, which associate with CLIP-170 and CLIP-115. Using RNA interference in HeLa cells, we show that the two CLASPs play redundant roles in regulating the density, length distribution and stability of interphase MTs. In HeLa cells, both CLASPs concentrate on the distal MT ends in a narrow region at the cell margin. CLASPs stabilize MTs by promoting pauses and restricting MT growth and shortening episodes to this peripheral cell region. We demonstrate that the middle part of CLASPs binds directly to EB1 and to MTs. Furthermore, we show that the association of CLASP2 with the cell cortex is MT independent and relies on its COOH-terminal domain. Both EB1- and cortex-binding domains of CLASP are required to promote MT stability. We propose that CLASPs can mediate interactions between MT plus ends and the cell cortex and act as local rescue factors, possibly through forming a complex with EB1 at MT tips.

Animals↗
PubMed2003

Dynamic behavior of paired claudin strands within apposing plasma membranes.

The tight junction (TJ) strand is a linear proteinaceous polymer spanning plasma membranes, and each TJ strand associates laterally with another TJ strand in the apposing membranes of adjacent cells to form "paired" TJ strands. Claudins have been identified as the major constituents of TJ strands, and when exogenously expressed in L fibroblasts, they polymerize into paired strands, which are morphologically similar to paired TJ strands in epithelia. Here, we show that a fusion protein of GFP with claudin-1 can also form similar paired strands in L fibroblasts, allowing us to directly observe individual paired claudin strands in live cells in real time. These paired strands showed more dynamic behavior than expected; they were occasionally broken and annealed, and dynamically associated with each other in both an end-to-side and side-to-side manner. Through this behavior of individual paired claudin strands, the network of strands was reorganized dynamically. Furthermore, fluorescence recovery after photobleaching analyses revealed that claudin molecules were not mobile within paired strands. Although these observations are not necessarily representative of TJ strands per se in epithelial cells, they provide important information on the structural and kinetic properties of TJ strands in situ with significant implications for barrier function of TJs.

Animals↗
PubMed2003

"Search-and-capture" of microtubules through plus-end-binding proteins (+TIPs).

The generation of a polarized microtubule organization is critically important for proper cellular functions, such as cell division, differentiation and migration. Microtubules themselves are highly dynamic structures, and this dynamic property is temporally and spatially regulated within cells, especially at their plus ends. To explain how microtubules set up and make contacts with cellular structures, a "search-and-capture" mechanism has been proposed, in which the microtubule plus ends dynamically search for and capture specific sites, such as mitotic kinetochores and cell cortex. To date, several classes of proteins have been shown to be associated with microtubule plus ends in a wide range of organisms from fungi to humans and to play critical roles in the "search-and-capture" mechanism. In this review, we overview our current understanding of the "plus-end-binding proteins" (+TIPs), including APC (adenomatous polyposis coli) tumor suppressor protein, cytoplasmic linker proteins (CLIPs), CLIP-associating proteins (CLASPs), cytoplasmic dynein/dynactin, and EB1, an APC-interacting protein.

Adenomatous Polyposis Coli Protein↗