Spinophilin is phosphorylated by Ca2+/calmodulin-dependent protein kinase II to regulate its binding to F-actin

Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10021, USA.
Journal of Neurochemistry (Impact Factor: 4.24). 08/2004; 90(2):317-24. DOI: 10.1111/j.1471-4159.2004.02491.x
Source: PubMed

ABSTRACT Spinophilin is a protein phosphatase-1- and actin-binding protein that modulates excitatory synaptic transmission and dendritic spine morphology. We have recently shown that the interaction of spinophilin with the actin cytoskeleton depends upon phosphorylation by protein kinase A. We have now found that spinophilin is phosphorylated by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in neurons. Ca(2+)/calmodulin-dependent protein kinase II, located within the post-synaptic density of dendritic spines, is known to play a role in synaptic plasticity and is ideally positioned to regulate spinophilin. Using tryptic phosphopeptide mapping, site-directed mutagenesis and microsequencing analysis, we identified two sites of CaMKII phosphorylation (Ser-100 and Ser-116) within the actin-binding domain of spinophilin. Phosphorylation by CaMKII reduced the affinity of spinophilin for F-actin. In neurons, phosphorylation at Ser-100 by CaMKII was Ca(2+) dependent and was associated with an enrichment of spinophilin in the synaptic plasma membrane fraction. These results indicate that spinophilin is phosphorylated by multiple kinases in vivo and that differential phosphorylation may target spinophilin to specific locations within dendritic spines.

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    • "In neurons, spinophilin regulates the actin cytoskeleton and microtubules by direct and indirect interactions ( Grossman et al., 2004 ; Ryan et al., 2005 ; Bielas et al., 2007 ). Although in DCs, actin and its regulation by Rac regulate DC – T cell interactions ( Benvenuti et al., 2004 ), Rac does not seem to be a target for spinophilin or the Rho – guanine nucleotide exchange factor with which spinophilin interacts ( Ryan et al., 2005 ). "
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    • "The affinity of spinophilin for F-actin is regulated by phosphorylation of the actin-binding domain, which can be mediated by PKA and CaMKII (Grossman et al., 2004; Hsieh-Wilson et al., 2003). In neurons, Ca 2+ -dependent phosphorylation by CaMKII reduces the affinity of spinophilin for actin and targets the protein to synaptic membrane fractions (Grossman et al., 2004). Expression studies in hippocampal neurons showed that Lcf localizes to the cell body and the dendritic shaft, where it associates with microtubules. "
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