• Molecules and Cells
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• v.42 no.8
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• pp.589-596
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• 2019

${\beta}Pix$ is a guanine nucleotide exchange factor for the Rho family small GTPases, Rac1 and Cdc42. It is known to regulate focal adhesion dynamics and cell migration. However, the in vivo role of ${\beta}Pix$ is currently not well understood. Here, we report the production and characterization of ${\beta}Pix$-KO mice. Loss of ${\beta}Pix$ results in embryonic lethality accompanied by abnormal developmental features, such as incomplete neural tube closure, impaired axial rotation, and failure of allantois-chorion fusion. We also generated ${\beta}Pix$-KO mouse embryonic fibroblasts (MEFs) to examine ${\beta}Pix$ function in mouse fibroblasts. ${\beta}Pix$-KO MEFs exhibit decreased Rac1 activity, and defects in cell spreading and platelet-derived growth factor (PDGF)-induced ruffle formation and chemotaxis. The average size of focal adhesions is increased in ${\beta}Pix$-KO MEFs. Interestingly, ${\beta}Pix$-KO MEFs showed increased motility in random migration and rapid wound healing with elevated levels of MLC2 phosphorylation. Taken together, our data demonstrate that ${\beta}Pix$ plays essential roles in early embryonic development, cell spreading, and cell migration in fibroblasts.

• 대한약리학회:학술대회논문집
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• 2006.11a
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• pp.63-63
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• 2006

• BMB Reports
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• v.54 no.7
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• pp.380-385
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• 2021

Proper targeting of the βPAK-interacting exchange factor (βPIX)/G protein-coupled receptor kinase-interacting target protein (GIT) complex into distinct cellular compartments is essential for its diverse functions including neurite extension and synaptogenesis. However, the mechanism for translocation of this complex is still unknown. In the present study, we reported that the conventional kinesin, called kinesin-1, can transport the βPIX/GIT complex. Additionally, βPIX bind to KIF5A, a neuronal isoform of kinesin-1 heavy chain, but not KIF1 and KIF3. Mapping analysis revealed that the tail of KIF5s and LZ domain of βPIX were the respective binding domains. Silencing KIF5A or the expression of a variety of mutant forms of KIF5A inhibited βPIX targeting the neurite tips in PC12 cells. Furthermore, truncated mutants of βPIX without LZ domain did not interact with KIF5A, and were unable to target the neurite tips in PC12 cells. These results defined kinesin-1 as a motor protein of βPIX, and may provide new insights into βPIX/GIT complex-dependent neuronal pathophysiology.

• Proceedings of the Zoological Society Korea Conference
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• 2001.10a
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• pp.210.2-210
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• 2001

No Abstract, See Full Text

• Proceedings of the Zoological Society Korea Conference
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• 2001.10a
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• pp.210.3-211
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• 2001

No Abstract, See Full Text

• Proceedings of the Microbiological Society of Korea Conference
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• 2004.05a
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• pp.141-146
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• 2004

SPIN90 was identified to farm molecular complex with $\betaPIX$, WASP and Nck. This complex shows that SPIN90 interacts with Nck in a manner dependent upon cell adhesion to extracellular matrix, but $SPIN90{\cdot}{\beta}PIX{\cdot}WASP$ complex was stable even in suspended cells. This suggests that SPIN90 serves as an adaptor molecule to recruit other proteins to Nck at focal adhesions. SPIN90 was phosphorylated by ERK1, which was, itself, activated by cell adhesion and platelet-derived growth factor. Such phosphorylation of SPIN90 likely promotes the interaction of the $SPIN90{\cdot}{\beta}PIX{\cdot}WASP$ complex and Nck. It thus appears that the interaction of the $SPIN90{\cdot}{\beta}PIX{\cdot}WASP$ complex with Nck is crucial for stable cell adhesion and can be dynamically modulated by SPIN90 phosphorylation that is dependent on cell adhesion and ERX activation. SPIN90 directly binds syndapin I, syndapin isoform II-1 and II-s via its PRD region in vitro, in vivo and also associates with endocytosis core components such as clathrin and dynamin. In neuron and fibroblast, SPIN90 colocalizes with syndapins as puntate form, consistent with a role for SPIN90 in clathrin-mediated endocytosis pathway. Overexpression of SPIN90 N-term inhibits receptor-mediated endocytosis. Interestingly, SPIN90 PRD, binding interface of syndapin, significantly blocks internalization of transferrin, demonstrating SPIN90 involvement in endocytosis in vivo by interacting syndapin. Depletion of endogenous SPIN90 by introducing $\alpha-SPIN90$ also blocks receptor-mediated endocytosis. Actin polymerization could generate farce facilitating the pinch-out event in endocytosis, detach newly formed endocytic vesicle from the plasma membrane or push out them via the cytosol on actin tails. Here we found that SPIN90 localizes to high actin turn over cortical area, actin-membrane interface and membrane ruffle in PDGF treated cells. Overexpression of SPIN90 has an effect on cortical actin rearrangement as filopodia induction and it is mediated by the Arp2/3 complex at cell periphery. Consistent with a role in actin organization, CFP-SPIN90 present in actin comet tail generated by PIP5 $kinase\gamma$ overexpression. Therefore this study suggests that SPIN90 is functional linker between endocytosis and actin cytoskeleton.

• Proceedings of the Zoological Society Korea Conference
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• 2001.10a
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• pp.210.1-210
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• 2001

No Abstract, See Full Text

• Macromolecular Research
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• v.17 no.2
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• pp.99-103
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• 2009

We evaluated the efficacy of pH-sensitive micelles, formed by methoxy poly(ethylene glycol)-b-poly($\beta$)-amino ester) (PEG-PAE), as carriers for paclitaxel (PIX), a drug currently used to treat various cancers. PTX was successful encapsulated by a film hydration method. Micelles encapsulated more than 70% of the PTX and the size of the PTX-encapsulated micelles (PTX-PM) was less than 150 nm. In vitro experiments indicated that the micelles were unstable below pH 6.5. After encapsulation of PTX within the micelles, dynamic light scattering (DLS) studies indicated that low pH had a similar demicellization effect. An in vitro release study indicated that PTX was slowly released at pH 7.4 (normal body conditions) but rapidly released under weakly acidic conditions (pH 6.0). We demonstrated the safety of micelles from in vitro cytotoxicity tests on HeLa cells and the in vivo anti-tumor activity of PTX-PM in B16F 10 tumor-bearing mice. We concluded that these pH-sensitive micelles have potential as carriers for anti-cancer drugs.