title: Protein kinase A and regulation of neonatal Nav1.5 expression in human breast cancer cells: activity-dependent positive feedback and cellular migration.
abstract: Voltage-gated Na(+) channels (VGSCs) are expressed in excitable cells (e.g. neurons and muscles), as well as in some classically 'non-excitable' cells (e.g. fibroblasts), and in carcinomas. In general, functional expression of VGSCs in plasma membrane (PM) is hierarchical and dynamic. Previously, we have shown that an activity-dependent positive feedback mechanism involving cAMP-dependent protein kinase A (PKA) plays a significant role in upregulation of VGSCs in strongly metastatic rat prostate cancer Mat-LyLu cells expressing Nav1.7. Here, we investigated the possible role of PKA in VGSC regulation and its functional consequences in strongly metastatic human breast cancer (BCa) MDA-MB-231 cells, where the neonatal splice form of Nav1.5 (nNav1.5) is the predominant VGSC present. Treatment with the PKA activator forskolin for 24h increased mRNA and PM protein levels of nNav1.5, without changing the total VGSC protein level. Opposite effects were obtained by application of the PKA inhibitor KT5720 or the highly specific VGSC blocker tetrodotoxin (TTX), the latter implying activity-dependent upregulation. We tested the possibility, therefore, that the activity dependence of VGSC (nNav1.5) expression involved PKA. Indeed, TTX pretreatment reduced the level of phosphorylated PKA and eliminated basal and PKA-stimulated cellular migration. These data suggested that activity-dependent positive feedback mediated by PKA plays an important role in the functional expression of nNav1.5 in BCa, and in turn, this enhances the cells' metastatic potential.
authors: Neuroscience Solution to Cancer Research Group, Division of Cell and Molecular Biology, Imperial College London, South Kensington Campus, London, UK.
authors: Athina-Myrto
authors: AM
authors: Chioni
authors: Dongmin
authors: D
authors: Shao
authors: Richard
authors: R
authors: Grose
authors: Mustafa B A
authors: MB
authors: Djamgoz
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology*; D002227:Carbazoles / Q000494:pharmacology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D025461:Feedback, Physiological; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007231:Infant, Newborn; D009124:Muscle Proteins / Q000235:genetics*; D062554:NAV1.5 Voltage-Gated Sodium Channel; D009361:Neoplasm Invasiveness; D010766:Phosphorylation / Q000187:drug effects; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D015222:Sodium Channels / Q000235:genetics*; D017154:Stromal Cells / Q000473:pathology; D013779:Tetrodotoxin / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D002227:Carbazoles; D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; D011758:Pyrroles; C568320:SCN5A protein, human; C568322:Scn5a protein, rat; D015222:Sodium Channels; D005576:Colforsin; D013779:Tetrodotoxin; C057416:KT 5720; D017868:Cyclic AMP-Dependent Protein Kinases