Densin-180 forms a ternary complex with the (alpha)-subunit of Ca2+/calmodulin-dependent protein kinase II and (alpha)-actinin.
Densin-180 is a transmembrane protein that is tightly associated with the postsynaptic density in CNS neurons and is postulated to function as a synaptic adhesion molecule. Here we report the identification of the alpha-subunit of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and alpha-actinin-4 as potential binding partners for the densin-180 intracellular ... segment. We demonstrate by yeast two-hybrid and biochemical assays that the intracellular portion of densin-180, the alpha-subunit of CaMKII (CaMKIIalpha), and alpha-actinin interact with each other at distinct binding sites and can form a ternary complex stabilized by multiple interactions. Densin-180 binds specifically to the association domain of CaMKIIalpha and does not bind with high affinity to holoenzymes of CaMKII that contain beta-subunit. The PDZ (PSD-95, DIg, Z0-1) domain of densin contributes to its binding to alpha-actinin. A distinct domain of alpha-actinin interacts with the kinase domains of both alpha- and beta-subunits of CaMKII. Autophosphorylation of CaMKII increases its affinity for densin-180 from an EC(50) of >1 micrometer to an EC(50) of <75-150 nM. In contrast, phosphorylation of densin-180 by CaMKII at serine-1397 only slightly decreases its affinity for CaMKII. The specific interaction of densin-180 with holoenzymes of CaMKII containing only alpha-subunit and the increased affinity of CaMKII for densin-180 after autophosphorylation suggest that densin-180 may be involved in localization of activated CaMKII synthesized in dendrites.
Mesh Terms:
Actinin, Animals, Binding Sites, Calcium-Calmodulin-Dependent Protein Kinase Type 2, Calcium-Calmodulin-Dependent Protein Kinases, Humans, Macromolecular Substances, Microfilament Proteins, Phosphorylation, Precipitin Tests, Prosencephalon, Protein Binding, Protein Structure, Tertiary, Protein Subunits, Rats, Recombinant Fusion Proteins, Sequence Analysis, Protein, Sialoglycoproteins, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Synaptosomes, Two-Hybrid System Techniques
Actinin, Animals, Binding Sites, Calcium-Calmodulin-Dependent Protein Kinase Type 2, Calcium-Calmodulin-Dependent Protein Kinases, Humans, Macromolecular Substances, Microfilament Proteins, Phosphorylation, Precipitin Tests, Prosencephalon, Protein Binding, Protein Structure, Tertiary, Protein Subunits, Rats, Recombinant Fusion Proteins, Sequence Analysis, Protein, Sialoglycoproteins, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Synaptosomes, Two-Hybrid System Techniques
J. Neurosci.
Date: Jan. 15, 2001
PubMed ID: 11160423
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