Regulation of Dendritogenesis via a Lipid-Raft-Associated Ca2+/Calmodulin-Dependent Protein Kinase CLICK-III/CaMKIγ

Abstract

Ca(2+) signaling plays a central role in activity-dependent regulation of dendritic arborization, but key molecular mechanisms downstream of calcium elevation remain poorly understood. Here we show that the C-terminal region of the Ca(2+)/calmodulin-dependent protein kinase CLICK-III (CL3)/CaMKIgamma, a membrane-anchored CaMK, was uniquely modified by two sequential lipidification steps: prenylation followed by a kinase-activity-regulated palmitoylation. These modifications were essential for CL3 membrane anchoring and targeting into detergent-resistant lipid microdomains (or rafts) in the dendrites. We found that CL3 critically contributed to BDNF-stimulated dendritic growth. Raft insertion of CL3 specifically promoted dendritogenesis of cortical neurons by acting upstream of RacGEF STEF and Rac, both present in lipid rafts. Thus, CL3 may represent a key element in the Ca(2+)-dependent and lipid-raft-delineated switch that turns on extrinsic activity-regulated dendrite formation in developing cortical neurons.

S-Palmitoylation of γ-Secretase Subunits Nicastrin and APH-1

“…S-Palmitoylation has been demonstrated as essential modification for raft localization of numerous cytosolic and transmembrane proteins (25,54,55). Our DRM fractionation studies reveal that S-palmitoylation contributes to, but is not absolutely required for, raft association of nicastrin and APH-1 (Fig.…”

“…Cysteines close to transmembrane domains or membrane-associated domains in non-integral membrane proteins are preferred S-palmitoylation sites, although no conserved motif has been identified (18). Palmitoylation modifies numerous neuronal proteins, including postsynaptic density protein PSD-95 (19), a-amino-3-hydroxyl-5-methyl-4-isoxazole propionic acid receptors (20), nicotinic ␣7 receptors (21), neuronal t-SNAREs SNAP-25, synaptobrevin 2 and synaptogagmin (22,23), neuronal growthassociated protein GAP-43 (24), protein kinase CLICK-III (CL3)/CaMKI␥ (25), ␤-secretase (26), and Huntingtin (27). Although palmitoylation can occur in vitro without the involvement of an enzyme, a family of palmitoyltransferases that specifically catalyze S-palmitoylation has been identified (28,29).…”

Ca2+/Calmodulin-dependent Protein Kinase IV-mediated LIM Kinase Activation Is Critical for Calcium Signal-induced Neurite Outgrowth

“…Although CaMKI has been shown to activate Rac (an upstream regulator of LIMK1) through activation of Rac-guanine nucleotide exchange factors, such as STEF and ␤PIX (46,47), CaMKI failed to activate LIMK1 in our coexpression experiments in Neuro-2a cells (Fig. 5A).…”

Ca2+/Calmodulin-dependent Protein Kinase Kinase β Is Regulated by Multisite Phosphorylation

“…In cortical neurons, CaMKK-CaMKI␣ and CaMKK-CaMKI␥ pathways have been implicated in the growth of axons and dendrites, respectively (13,48). In addition, regulation of CaMKI␥ by CaMKK has also been implicated in the early stages of axon formation (12).…”