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At Caco-2 epithelial cell adherens junctions, cadherins (E-cadherin, red) colocalize (yellow) with AKAP79/150 (green), a scaffold protein that organizes a signaling complex containing PKA, PKC, and protein phosphatase 2B-calcineurin that has been shown to regulate phosphorylation of plasma membrane receptors and ion channels. The inset shows that these proteins, AKAP79/150 (green) and N-cadherin (magenta), also colocalize (white) in hippocampal neurons at postsynaptic dendritic spines of excitatory synaptic junctions. Work by Gorski et al. (Mol. Biol. Cell [2005] 16, 3577-3593; published online before print as 10.1091/mbc.E05-02-0134) shows that AKAP79/150 and cadherins interact directly by binding of the AKAP N-terminus to the cytoplasmic domain of cadherins, thereby recruiting the AKAP and its bound signaling enzymes to junctional assemblies containing cadherins and β-catenin in both neurons and epithelial cells. In neurons, glutamate receptor stimulation of Ca²⁺ signaling pathways involving protein phosphatase 2B-calcineurin and PKA that are implicated in long-term depression of excitatory synaptic transmission and dendritic spine actin reorganization disrupted AKAP-cadherin interactions, leading to loss of the AKAP, but not cadherins and β-catenin, from synapses. This neuronal regulation of AKAP79/150 targeting to cadherins may be important in coordinating signaling pathways regulating both functional and structural synaptic modifications underlying excitatory plasticity. These studies demonstrate novel signaling interactions for both AKAPs and cadherins and continue to elucidate fascinating parallels between epithelial and neuronal cell biology. (Image; Jessica A. Gorski, University of Colorado at Denver and Health Sciences Center)

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Copyright © 2005 by The American Society for Cell Biology.