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

Abstract

Actin cytoskeletal remodeling is essential for cell morphological changes, motility, and migration. In neurons, actin filament remodeling plays a critical role in the control of neurite outgrowth and guidance (1-3). A number of actin-binding proteins and their upstream signaling molecules have been implicated in the regulation of neurite extension, retraction, and guidance (1-3). Cofilin is an actin-binding protein that plays a key role in controlling actin filament dynamics and reorganization by stimulating the depolymerization and severing of actin filaments (4, 5). These activities of cofilin are negatively regulated by phosphorylation at Ser-3 by LIM kinases (LIMKs) 2 (6, 7), and the inactive Ser-3-phosphorylated cofilin (P-cofilin) is reactivated by dephosphorylation catalyzed by protein phosphatases of the Slingshot (SSH) family (8, 9). LIMK1 is activated by phosphorylation at Thr-508 (in the kinase catalytic domain) by ROCK and PAK, downstream kinases of the Rho family small GTPases Rho, Rac, and Cdc42 (10 -12), or phosphorylation at Ser-323 (outside the catalytic domain) by mitogen-activated protein kinase-activated protein kinase-2, a kinase downstream of p38 mitogen-activated protein kinase (13). Several lines of evidence suggest that cofilin and its upstream regulators, LIMKs and SSHs, play crucial roles in controlling neurite outgrowth and guidance (14 -21). Calcium ion is a critical second messenger that mediates a variety of neuronal functions, including neurite outgrowth, axonal guidance, neuronal differentiation, synaptic plasticity, and memory formation. Numerous Ca 2ϩ -evoked responses are mediated by the Ca 2ϩ

LIM Kinase, a Newly Identified Regulator of Presynaptic Remodeling by Rod Photoreceptors After Injury

“…In addition, the relationship between the LIMK-cofilin pathway and Ca 2þ is not well understood and has been reported to vary under different circumstances in neurons. 96,97 In contrast to the 7-hour retraction data, at 3 days in culture, a period when process outgrowth occurs, combined LIMK inhibition and Ca 2þ influx blockage showed significantly further inhibition than LIMK inhibition alone. As actomyosin contraction is unlikely to contribute to process growth directly, one possible role of Ca 2þ signaling in neuritic growth is that elevated intracellular Ca 2þ upregulates LIMK activity through a Ca 2þ -calmodulin-CaMKIV-LIMK signaling pathway.…”

“…As actomyosin contraction is unlikely to contribute to process growth directly, one possible role of Ca 2þ signaling in neuritic growth is that elevated intracellular Ca 2þ upregulates LIMK activity through a Ca 2þ -calmodulin-CaMKIV-LIMK signaling pathway. 97 Additionally, slingshot (SSH), the major phosphatase for cofilin, has been reported to be under regulation by Ca 2þ signaling. 98,99 Thus, it is also possible that under combined treatments, the phosphatase (SSH) activity increased due to Ca 2þ blockage by Nc while the kinase (LIMK) activity was inhibited directly by BMS-5.…”

Distinct Effects of Voltage- and Store-dependent Calcium Influx on Stretch-induced Differentiation and Growth in Vascular Smooth Muscle

“…Inhibition of CaMK has been reported to inhibit KCl but not ionomycin-induced RhoA activation in vascular smooth muscle cells (31) and also to inhibit ionomycin-induced LIM kinase activity in neuroblastoma cells (24). Depending on the mode of Ca 2ϩ elevation, CaMK activity may therefore affect the Rho pathway and downstream ROK activity and cofilin phosphorylation.…”

“…One such possibility is direct phosphorylation of LIM kinase by CaMKIV, which has recently been shown in neuroblastoma cells (24). To test this, portal vein cells were incubated with the ROK inhibitor Y27632 and the CaMK inhibitor KN93, or both, and activated by KCl.…”

An α7 nicotinic receptor-G protein pathway complex regulates neurite growth in neural cells*

“…Drug concentrations were determined based on published studies (Chan and Quik, 1993;Jian et al, 1994;Strittmatter et al, 1994a;Owen and Bird, 1995;Swarzenski et al, 1996;Hilmas et al, 2001;Kano et al, 2002;Hruska and Nishi, 2007;Lopes et al, 2007;Takemura et al, 2009): a-Bungarotoxin (Bgtx) (10 nM, Sigma), nicotine (Nic) (50 mM, Sigma), PNU282987 (PNU) (50 mM, Sigma), pertussis toxin (Ptx) (1 mM, Calbiochem), mastoparan (30 mM, Tocris), FK506 (25 nM, Tocris), KN-93 (1 mM, Tocris), calmidazolium (CMZ) (1 mM, Enzo), acetylcholine (ACh) (100 mM, Sigma) and KYNA (1:100 mM, Sigma). The duration of the chronic drug treatment described in this study is 4 days unless otherwise noted.…”