α-Catenin is a key cell adhesion protein that is thought to indispensably link the cadherin-based adhesion complex to the actin cytoskeleton.α-catenin appears to play a central role in cell-cell contact formation.Although dilated cardiomyopathy, interaction with adherens junction protein, biochemical, structural and live-cell imaging studies of α-catenin are observed in cardiomyocytes and tissues in vivo or in vitro, its physiological function and relationships with expression of intercalated disc proteins in HL-1 cell line remain unknow.The objective of this study was to assess the expression and/or localization of intercalated disks proteins,and communication and electric conduction of gap junction in α-catenin knockout HL-1 cells.HL-1 mouse myocyte cells were transfected with α-catenin siRNA and negative contorl(NC) siRNA.Expression of intercalated disks proteins was characterized by immunoblotting and Immuno-fluorescence microscopy in α-catenin siRNA and NC siRNA transfected HL-1 cells.Proliferation of cells was counted after trypsinization using a hemocytometer.Apoptotic or necrotic of HL-1 cells were determined with annexin-V-Fluos staining assay kit.Cardioyocyte-cardiomyocyte coupling was determined by Lucifer yellow(LY) dye transfer.Electrical conduction of gap junctions were studied by microelectrode arrays(MEA).With the concetration of α-catenin siRNA gradually increase, anti-α-catenin antibody expression in HL-1 cell line was reduced gradually and showed significant dose-dependence decreasing effect.Number of HL-1 cells were reduced at 96h and 120h in α-catenin transfected HL-lcells,even decreased to 50% compared with none siRNA group and NC group.However, apoptosis or necrosis of HL-1 cardiomyocytes were exhibited at 48h and 72h in α-catenin transfected HL-lcells,and showed early than reduction of number of cells.Expression levels of other adherens junction (β-catenin, γ-catenin), gap junction (Cx43) and ZO-1 proteins were significantly decrease at 96h in α-catenin siRNA transfected HL-1 cells,but not change for expression level of desmosome (DPK) protein.The gap junctions at the intercalated disc were smaller for LY dye transfer and electrical conduction velocities were depressed obviously in α-catenin knockout HL-1 cells.Above these results indicated that inactivation of α-catenin protein expression showed significat dose-dependent manner and time-dependent manner and α-catenin protein expression in cell level was inactivated by α-catenin gene knockout in HL-1 cells in vitro;α-Catenin adhesion molecular may play vrery critical role in the maintain of number, proliferation,and survival of normal HL-1 cardiomyocytes and functions.α-Catenin may become one of mainly controlling molecular for intercalated disc protein of HL-1 cells or play a central role in cell-cell contact formation;Normal concentration of α-catenin at intercaled disc in H1-1 cardiomyocytes also may play an important role in maintain of intercellular communication and in controlled conduction of electrical excitation, electrophysiology function,and cell-cell electrical coupling.