EphB Receptors Regulate Dendritic Spine Morphogenesis through the Recruitment/Phosphorylation of Focal Adhesion Kinase and RhoA Activation

Tissue cells respond to changes in tensional forces with proliferation or death through the control of RhoA. However, the response coupling mechanisms that link force with RhoA activation are poorly understood. We found that tension applied to fibronectin-coated microbeads caused recruitment of all three isoforms of the Shc adapter (p66 Shc , p52 Shc , and p46 Shc ) to adhesion complexes. The Shc PTB domain was necessary and sufficient for this recruitment, and screening studies revealed the direct interactions with the FERM domain of focal adhesion kinase (FAK) that were required for Shc translocation to adhesion complexes. The FAK/p66 Shc complex specifically bound and activated the Rho guanyl exchange factors (GEFs) p115-RhoGEF and GEF-H1, leading to tension-induced RhoA activation. In contrast, the FAK/p52 Shc complex bound SOS1 but not the Rho GEFs to mediate tension-induced Ras activation. Nuclear translocation and activation of the YAP/TAZ transcription factors on firm substrates required the FAK/p66 Shc /Rho GEF complex, and both proliferation on firm substrates and anoikis in suspension required signaling through p66 Shc and its associated Rho GEFs. These studies reveal the binary and exclusive assignment of p66 Shc and p52 Shc to tension-induced Rho or Ras signals, respectively, and suggest an integrated role for the two Shc isoforms in coordinating the cellular response to mechanical stimuli.

Download Full-text

The Headpiece Domain of Dematin Regulates Cell Shape, Motility, and Wound Healing by Modulating RhoA Activation

Molecular and Cellular Biology ◽

10.1128/mcb.00237-08 ◽

2008 ◽

Vol 28 (15) ◽

pp. 4712-4718 ◽

Cited By ~ 10

Author(s):

Morvarid Mohseni ◽

Athar H. Chishti

Keyword(s):

Wound Healing ◽

Focal Adhesion Kinase ◽

Signaling Pathways ◽

Focal Adhesion ◽

Mouse Skin ◽

Fiber Formation ◽

Negative Regulator ◽

Rhoa Activation ◽

Primary Mouse

ABSTRACT RhoA is known to participate in cytoskeletal remodeling events through several signaling pathways, yet the precise mechanism of its activation remains unknown. Here, we provide the first evidence that dematin functions upstream of RhoA and regulates its activation. Primary mouse embryonic fibroblasts were generated from a dematin headpiece domain null (HPKO) mouse, and the visualization of the actin morphology revealed a time-dependent defect in stress fiber formation, membrane protrusions, cell motility, and cell adhesion. Rescue experiments using RNA interference and transfection assays revealed that the observed phenotypes are due to a null effect and not a gain of function in the mutant fibroblasts. In vivo wounding of adult HPKO mouse skin showed a decrease in wound healing (reepithelialization and granulation) compared to the wild-type control. Biochemical analysis of the HPKO fibroblasts revealed a sustained hyperphosphorylation of focal adhesion kinase (FAK) at tyrosine 397 as well as a twofold increase in RhoA activation. Inhibition of both RhoA and FAK signaling using C3 toxin and FRNK (focal adhesion kinase nonrelated kinase), respectively, revealed that dematin acts upstream of RhoA. Together, these results unveil a new function of dematin as a negative regulator of the RhoA activation pathway with physiological implications for normal and pathogenic signaling pathways.

Download Full-text

Focal Adhesion Kinase Acts Downstream of EphB Receptors to Maintain Mature Dendritic Spines by Regulating Cofilin Activity

Journal of Neuroscience ◽

10.1523/jneurosci.4681-08.2009 ◽

2009 ◽

Vol 29 (25) ◽

pp. 8129-8142 ◽

Cited By ~ 93

Author(s):

Y. Shi ◽

C. G. Pontrello ◽

K. A. DeFea ◽

L. F. Reichardt ◽

I. M. Ethell

Keyword(s):

Focal Adhesion Kinase ◽

Focal Adhesion ◽

Dendritic Spines ◽

Ephb Receptors

Download Full-text

EphB Maintains Dendritic Spine Morphology through Focal Adhesion Kinase

Journal of Neuroscience ◽

10.1523/jneurosci.4155-09.2009 ◽

2009 ◽

Vol 29 (42) ◽

pp. 13091-13093 ◽

Cited By ~ 4

Author(s):

Y. Chen ◽

W.-Y. Fu

Keyword(s):

Focal Adhesion Kinase ◽

Focal Adhesion ◽

Dendritic Spine ◽

Spine Morphology ◽

Dendritic Spine Morphology

Download Full-text

Early signalling events of autophagy

Essays in Biochemistry ◽

10.1042/bse0550001 ◽

2013 ◽

Vol 55 ◽

pp. 1-15 ◽

Cited By ~ 16

Author(s):

Laura E. Gallagher ◽

Edmond Y.W. Chan

Keyword(s):

Protein Kinase ◽

Focal Adhesion Kinase ◽

Focal Adhesion ◽

Mammalian Cells ◽

Mammalian Target Of Rapamycin ◽

Interacting Protein ◽

The Core ◽

Autophagy Gene ◽

Autophagy Induction ◽

Cellular Pathways

Autophagy is a conserved cellular degradative process important for cellular homoeostasis and survival. An early committal step during the initiation of autophagy requires the actions of a protein kinase called ATG1 (autophagy gene 1). In mammalian cells, ATG1 is represented by ULK1 (uncoordinated-51-like kinase 1), which relies on its essential regulatory cofactors mATG13, FIP200 (focal adhesion kinase family-interacting protein 200 kDa) and ATG101. Much evidence indicates that mTORC1 [mechanistic (also known as mammalian) target of rapamycin complex 1] signals downstream to the ULK1 complex to negatively regulate autophagy. In this chapter, we discuss our understanding on how the mTORC1–ULK1 signalling axis drives the initial steps of autophagy induction. We conclude with a summary of our growing appreciation of the additional cellular pathways that interconnect with the core mTORC1–ULK1 signalling module.

Download Full-text