scholarly journals Synapses are regulated by the cytoplasmic tyrosine kinase Fer in a pathway mediated by p120catenin, Fer, SHP-2, and β-catenin

2008 ◽  
Vol 183 (5) ◽  
pp. 893-908 ◽  
Author(s):  
Seung-Hye Lee ◽  
I.-Feng Peng ◽  
Yu Gie Ng ◽  
Masahiro Yanagisawa ◽  
Shernaz X. Bamji ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Tyrosine Kinase ◽  
Synaptic Vesicle ◽  
Tyrosine Phosphorylation ◽  
Protein Phosphatase ◽  
Synaptic Vesicles ◽  
Synapse Formation ◽  
Excitatory Synapse ◽  
Synaptic Development ◽  
And Function

Localization of presynaptic components to synaptic sites is critical for hippocampal synapse formation. Cell adhesion–regulated signaling is important for synaptic development and function, but little is known about differentiation of the presynaptic compartment. In this study, we describe a pathway that promotes presynaptic development involving p120catenin (p120ctn), the cytoplasmic tyrosine kinase Fer, the protein phosphatase SHP-2, and β-catenin. Presynaptic Fer depletion prevents localization of active zone constituents and synaptic vesicles and inhibits excitatory synapse formation and synaptic transmission. Depletion of p120ctn or SHP-2 similarly disrupts synaptic vesicle localization with active SHP-2, restoring synapse formation in the absence of Fer. Fer or SHP-2 depletion results in elevated tyrosine phosphorylation of β-catenin. β-Catenin overexpression restores normal synaptic vesicle localization in the absence of Fer or SHP-2. Our results indicate that a presynaptic signaling pathway through p120ctn, Fer, SHP-2, and β-catenin promotes excitatory synapse development and function.

scholarly journals BDNF mobilizes synaptic vesicles and enhances synapse formation by disrupting cadherin–β-catenin interactions

2006 ◽  
Vol 174 (2) ◽  
pp. 289-299 ◽  
Author(s):  
Shernaz X. Bamji ◽  
Beatriz Rico ◽  
Nikole Kimes ◽  
Louis F. Reichardt
Keyword(s):  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Hippocampal Neurons ◽  
Molecular Mechanisms ◽  
Synapse Formation ◽  
Time Lapse ◽  
Synapse Density ◽  
Vesicle Mobility ◽  
Small Clusters ◽  
Vertebrate Central Nervous System

Neurons of the vertebrate central nervous system have the capacity to modify synapse number, morphology, and efficacy in response to activity. Some of these functions can be attributed to activity-induced synthesis and secretion of the neurotrophin brain-derived neurotrophic factor (BDNF); however, the molecular mechanisms by which BDNF mediates these events are still not well understood. Using time-lapse confocal analysis, we show that BDNF mobilizes synaptic vesicles at existing synapses, resulting in small clusters of synaptic vesicles “splitting” away from synaptic sites. We demonstrate that BDNF's ability to mobilize synaptic vesicle clusters depends on the dissociation of cadherin–β-catenin adhesion complexes that occurs after tyrosine phosphorylation of β-catenin. Artificially maintaining cadherin–β-catenin complexes in the presence of BDNF abolishes the BDNF-mediated enhancement of synaptic vesicle mobility, as well as the longer-term BDNF-mediated increase in synapse number. Together, this data demonstrates that the disruption of cadherin–β-catenin complexes is an important molecular event through which BDNF increases synapse density in cultured hippocampal neurons.

scholarly journals N-cadherin: stabilizing synapses

2010 ◽  
Vol 189 (3) ◽  
pp. 397-398 ◽  
Author(s):  
Jyothi Arikkath
Keyword(s):  
Cell Adhesion ◽  
Cell Adhesion Molecule ◽  
Synapse Formation ◽  
Structure And Function ◽  
Cellular Mechanisms ◽  
Central Neurons ◽  
Spine Stabilization ◽  
Spine Structure ◽  
And Function ◽  
Spine Dynamics

Spines are sites of excitatory synapse formation in central neurons. Alterations in spine structure and function are widely believed to actively contribute to the cellular mechanisms of learning and memory. In this issue, Mendez et al. (2010. J. Cell Biol. doi:10.1083/jcb.201003007) demonstrate a pivotal role for the cell adhesion molecule N-cadherin in activity-mediated spine stabilization, offering a new mechanism for how spine dynamics and stability are regulated by activity in central neurons.

Activation of TrkA tyrosine kinase in embryonal carcinoma cells promotes cell compaction, independently of tyrosine phosphorylation of catenins

2000 ◽  
Vol 113 (9) ◽  
pp. 1601-1610
Author(s):  
M. Cozzolino ◽  
B. Giovannone ◽  
A. Serafino ◽  
K. Knudsen ◽  
A. Levi ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Tyrosine Kinases ◽  
Embryonal Carcinoma ◽  
Receptor Tyrosine Kinases ◽  
Mdck Cells ◽  
Current Evidence ◽  
Tyrosine Kinase Receptor ◽  
Beta Catenin

Cadherins are transmembrane receptors whose extracellular domain mediates homophilic cell-cell interactions, while their cytoplasmic domain associates with a family of proteins known as catenins. Although the mechanisms that regulate the assembly and functional state of cadherin-catenin complexes are poorly understood, current evidence supports a role for protein tyrosine kinase activity in regulating cell adhesion and migration. Tyrosine phosphorylation of catenins is thought to mediate loss of intercellular adhesion promoted by activation of receptor tyrosine kinases in epithelial cells. Here, we show that activation of ectopically expressed TrkA, the tyrosine kinase receptor for nerve growth factor (NGF), stimulates embryonal carcinoma P19 cells to develop extensive intercellular contacts and to assemble into closely packed clusters. Thus, activation of receptor tyrosine kinases can differentially regulate adhesiveness by cell-type-specific mechanisms. Furthermore, activation of TrkA in P19 and epithelial MDCK cells induces tyrosine phosphorylation of p120(ctn) and of beta-catenin, irrespective of the elicited cellular response. The selective Src tyrosine kinase inhibitor PP2, however, suppresses NGF- or HGF-induced tyrosine phosphorylation of catenins in both P19 and MDCK cells without interfering with the acquisition of a compacted or scattered phenotype. These findings provide a cogent argument for considering that tyrosine phosphorylation of catenins is dispensable for their interaction with cadherins and, ultimately, for the modulation of cadherin-based cell adhesion by receptor tyrosine kinases.

scholarly journals Normal Biogenesis and Cycling of Empty Synaptic Vesicles in Dopamine Neurons of Vesicular Monoamine Transporter 2 Knockout Mice

2005 ◽  
Vol 16 (1) ◽  
pp. 306-315 ◽  
Author(s):  
Benjamin G. Croft ◽  
Gabriel D. Fortin ◽  
Amadou T. Corera ◽  
Robert H. Edwards ◽  
Alain Beaudet ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Knockout Mice ◽  
Synaptic Vesicles ◽  
Dopamine Neurons ◽  
Vesicular Monoamine Transporter ◽  
Wild Type ◽  
Monoamine Transporter ◽  
Vesicle Biogenesis ◽  
And Function ◽  
Activity Dependent

The neuronal isoform of vesicular monoamine transporter, VMAT2, is responsible for packaging dopamine and other monoamines into synaptic vesicles and thereby plays an essential role in dopamine neurotransmission. Dopamine neurons in mice lacking VMAT2 are unable to store or release dopamine from their synaptic vesicles. To determine how VMAT2-mediated filling influences synaptic vesicle morphology and function, we examined dopamine terminals from VMAT2 knockout mice. In contrast to the abnormalities reported in glutamatergic terminals of mice lacking VGLUT1, the corresponding vesicular transporter for glutamate, we found that the ultrastructure of dopamine terminals and synaptic vesicles in VMAT2 knockout mice were indistinguishable from wild type. Using the activity-dependent dyes FM1-43 and FM2-10, we also found that synaptic vesicles in dopamine neurons lacking VMAT2 undergo endocytosis and exocytosis with kinetics identical to those seen in wild-type neurons. Together, these results demonstrate that dopamine synaptic vesicle biogenesis and cycling are independent of vesicle filling with transmitter. By demonstrating that such empty synaptic vesicles can cycle at the nerve terminal, our study suggests that physiological changes in VMAT2 levels or trafficking at the synapse may regulate dopamine release by altering the ratio of fillable-to-empty synaptic vesicles, as both continue to cycle in response to neural activity.

scholarly journals Tyrosine Phosphorylation and Src Family Kinases Control Keratinocyte Cell–Cell Adhesion

1998 ◽  
Vol 141 (6) ◽  
pp. 1449-1465 ◽  
Author(s):  
Enzo Calautti ◽  
Sara Cabodi ◽  
Paul L. Stein ◽  
Mechthild Hatzfeld ◽  
Nancy Kedersha ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Structural Changes ◽  
Regulatory Function ◽  
Kinase Inhibition ◽  
Tyrosine Kinase Inhibition ◽  
Primary Mouse ◽  
Keratinocyte Cell ◽  
E Cadherin

In their progression from the basal to upper differentiated layers of the epidermis, keratinocytes undergo significant structural changes, including establishment of close intercellular contacts. An important but so far unexplored question is how these early structural events are related to the biochemical pathways that trigger differentiation. We show here that β-catenin, γ-catenin/plakoglobin, and p120-Cas are all significantly tyrosine phosphorylated in primary mouse keratinocytes induced to differentiate by calcium, with a time course similar to that of cell junction formation. Together with these changes, there is an increased association of α-catenin and p120-Cas with E-cadherin, which is prevented by tyrosine kinase inhibition. Treatment of E-cadherin complexes with tyrosine-specific phosphatase reveals that the strength of α-catenin association is directly dependent on tyrosine phosphorylation. In parallel with the biochemical effects, tyrosine kinase inhibition suppresses formation of cell adhesive structures, and causes a significant reduction in adhesive strength of differentiating keratinocytes. The Fyn tyrosine kinase colocalizes with E-cadherin at the cell membrane in calcium-treated keratinocytes. Consistent with an involvement of this kinase, fyn-deficient keratinocytes have strongly decreased tyrosine phosphorylation levels of β- and γ-catenins and p120-Cas, and structural and functional abnormalities in cell adhesion similar to those caused by tyrosine kinase inhibitors. Whereas skin of fyn−/− mice appears normal, skin of mice with a disruption in both the fyn and src genes shows intrinsically reduced tyrosine phosphorylation of β-catenin, strongly decreased p120-Cas levels, and important structural changes consistent with impaired keratinocyte cell adhesion. Thus, unlike what has been proposed for oncogene-transformed or mitogenically stimulated cells, in differentiating keratinocytes tyrosine phosphorylation plays a positive role in control of cell adhesion, and this regulatory function appears to be important both in vitro and in vivo.

A Pyk2–Vav1 complex is recruited to β3-adhesion sites to initiate Rho activation

2009 ◽  
Vol 420 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Chunlei Gao ◽  
Scott D. Blystone
Keyword(s):  
Cell Adhesion ◽  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Fluorescent Protein ◽  
Rho Gtpase ◽  
Adaptor Protein ◽  
Direct Interaction ◽  
Nucleotide Exchange ◽  
Tyrosine Kinase 2

Integrin αvβ3-mediated adhesion of haemopoietic cells to vitronectin results in β3 tyrosine phosphorylation and Rho activation which is necessary for adhesion. Previously, we have shown that the RhoGEF (Rho guanine-nucleotide-exchange factor) Vav1 could associate indirectly with αvβ3 during leucocyte adhesion to vitronectin. In the present study, we have identified the non-receptor tyrosine kinase Pyk2 (proline-rich tyrosine kinase 2) as the adaptor protein that links Vav1 with αvβ3. The association of Pyk2 and Vav1 with β3 relies on the presence of Tyr747 in β3, the primary site of β3 phosphorylation. However, association of Pyk2 with Vav1 is independent of β3 tyrosine phosphorylation. Formation of a Pyk2–Vav1 complex occurs upon cell adhesion and Pro717 of Pyk2 plays a key role in Pyk2 interaction with Vav1. Utilizing purified recombinant proteins, we confirmed the direct interaction between Pyk2 and Vav1 In vitro. Cells transfected with GFP (green fluorescent protein)–Pyk2-P717A demonstrated severely suppressed cytoskeletal reorganization, impaired Vav1 recruitment, decreased Rho GTPase activation and loss of cell adhesion. Using siRNA (small interfering RNA) to specifically reduce Pyk2 levels in cells resulted in disrupted association between Vav1 and β3 and impaired cell adhesion. These results indicate that Pyk2 is a critical signalling molecule downstream of β3 integrin tyrosine phosphorylation and mediates Vav1 recruitment to accomplish actin reorganization necessary for adhesion.

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