title: 131I-MIBG targeting of neuroblastoma cells is acutely enhanced by KCl stimulation through the calcium/calmodulin-dependent kinase pathway.
abstract: The efficacy of (131)I-metaiodobenzylguanidine (MIBG) therapy relies on norepinephrine transporter (NET) function. The ionic make-up of the extracellular fluid critically controls neuronal cell activity and can also affect substrate transport. In this study, we explored the effect of treatment with elevated KCl concentration on MIBG uptake in SK-N-SH neuroblastoma cells. KCl stimulation caused a rapid increase of (131)I-MIBG uptake in a manner that was calcium-dependent and accompanied by activation of calcium/calmodulin-dependent protein kinase (CaMK)II. The effect was completely abolished by KN93, an inhibitor of CaMKI, II, and IV. STO609, a selective inhibitor of CaMK kinase required for activation of CaMKI and IV, but not CaMKII, only modestly attenuated the response. The KCl effect was also completely abrogated by ML7, a selective inhibitor of myosin light chain kinase (MLCK). This restricted form of CaMK activates myosin, which is required for vesicle trafficking. Saturation kinetic analysis revealed KCl stimulation to increase maximal transport velocity without affecting substrate affinity. In conclusion, KCl stimulation rapidly upregulates NET function through the CaMK pathway via activation of CaMKII and MLCK. These findings allow a better understanding of how NET function is acutely modulated by the ionic environment, which in turn may ultimately help improve the efficacy of (131)I-MIBG therapy.
authors.affiliation: Department of Nuclear Medicine, Konkuk University Medical Center, Research Institute of Biomedical Science, Konkuk University School of Medicine, Seoul, Korea.
authors.forename: Hyun Woo
authors.initials: HW
authors.lastname: Chung
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Park
authors.forename: Eun Jeong
authors.initials: EJ
authors.lastname: Lee
authors.forename: Kyung-Ho
authors.initials: KH
authors.lastname: Jung
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Paik
authors.forename: Kyung-Han
authors.initials: KH
authors.lastname: Lee
mesh_terms: D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D045744:Cell Line, Tumor; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D009447:Neuroblastoma / Q000000981:diagnostic imaging* / Q000201:enzymology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011189:Potassium Chloride / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*
chemical_list: D002147:Calmodulin; D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine; D011189:Potassium Chloride; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009219:Myosin-Light-Chain Kinase