Cytosolic Targeting Domains of γ and δ Calmodulin-dependent Protein Kinase II

Abstract

Ca2؉ /calmodulin-dependent protein kinase II (CaMK-II) isozyme variability is the result of alternative usage of variable domain sequences. Isozyme expression is cell type-specific to transduce the appropriate Ca 2؉ signals. We have determined the subcellular targeting domain of ␦ E CaMK-II, an isozyme that induces neurite outgrowth, and of a structurally similar isozyme, ␥ C CaMK-II, which does not induce neurite outgrowth. ␦ E CaMK-II co-localizes with filamentous actin in the perinuclear region and in cellular extensions. In contrast, ␥ C CaMK-II is uniformly cytosolic. Constitutively active ␦ E CaMK-II induces F-actin-rich extensions, thereby supporting a functional role for its localization. C-terminal constructs, which lack central variable domain sequences, can oligomerize and localize like full-length ␦ E and ␥ C CaMK-II. Central variable domains themselves are monomeric and have no targeting capability. The C-terminal 95 residues of ␦ CaMK-II also has no targeting capability but can efficiently oligomerize. These findings define a targeting domain for ␥ and ␦ CaMK-IIs that is in between the central variable and association domains. This domain is responsible for the subcellular targeting differences between ␥ and ␦ CaMK-IIs.

Activity-Dependent Regulation of Calcium/Calmodulin-Dependent Protein Kinase II Localization: Figure 1.

“…A highly selective cell-permeable peptide inhibitor of CaMKII [antCNt (Chang et al, 1998;Fink et al, 2003)] and downregulation of ␤-CaMKII with siRNA reduced movement of neuritic branches and decreased arborization. An ␣/␤-CaMKII chimera with partial actin binding produces a partial effect on the size of the dendritic arbor (Fink et al, 2003), and non-neuronal isoforms with partial actin binding produced actin-rich neurite extensions (Caran et al, 2001). The findings are consistent with a need for actin localization for the kinase to affect neurite activity.…”

The non-excitable smooth muscle: Calcium signaling and phenotypic switching during vascular disease

“…To date, there are 13 recognized CaMKIIγ splice variants. Similarly, 15 splice variants have been identified for the δ gene [29]. Both CaMKIIγ and CaMKIIδ are ubiquitously expressed with the highest levels observed in peripheral tissue [134].…”

Calcium/calmodulin-dependent protein kinase II-δ isoform regulation of vascular smooth muscle cell proliferation

“…Separate studies identified a cytosolic targeting domain in specific ␥ and ␦ isoforms (6). Because CaMKII is expressed as large homo-and heteromultimeric holoenzymes, the subunit composition may confer subcellular targeting and specific protein interactions directing enzymatic activity to specific cellular compartments and functions (4,6,43).…”