title: The Effects of Swiprosin-1 on the Formation of Pseudopodia-Like Structures and β-Adrenoceptor Coupling in Cultured Adult Rat Ventricular Cardiomyocytes.
abstract: BACKGROUND
  Recent findings suggest that adult terminally differentiated cardiomyocytes adapt to stress by cellular de- and redifferentiation. In the present study we tested the hypothesis that swiprosin-1 is a key player in this process. Furthermore, the relationship between swiprosin-1 and β-adrenoceptor coupling was analyzed.
  
  
  METHODS
  In order to study the function of swiprosin-1 in adult rat ventricular cardiomyocytes (ARVC) they were isolated and cultured in a medium containing 20% fetal calf serum (FCS). Changes in cell morphology of ARVC during cultivation were quantified by light and confocal laser scan microscopy. Small interfering RNA (siRNA) was used to reduce the expression of swiprosin-1. The impact of calcium on swiprosin-1 dependent processes was investigated with Bapta-AM. Immunoblot techniques and qRT-PCR were performed to measure mRNA and protein expression.
  
  
  RESULTS
  In culture, ARVC first lost their contractile elements, which was followed by a formation of pseudopodia-like structures (spreading). Swiprosin-1 was detected in ARVC at all time points. However, swiprosin-1 expression was increased when ARVC started to spread. Reduction of swiprosin-1 expression with siRNA delayed ARVC spreading. Similarly, Bapta-AM attenuated swiprosin-1 expression and spreading of ARVC. Furthermore, swiprosin-1 expression correlated with the expression of G protein-coupled receptor kinase 2 (GRK2). Moreover, silencing of swiprosin-1 was associated with a down regulation of GRK2 and caused a sensitization of β-adrenergic receptors.
  
  
  CONCLUSIONS
  Swiprosin-1 is required for ARVC to adapt to culture conditions. Additionally, it seems to be involved in the desensitization of β-adrenergic receptors. Assuming that ARVC adapt to cardiac stress in a similar way, swiprosin-1 may play a key role in cardiac remodeling.
authors.affiliation: Institute of Physiology, Justus-Liebig-University, Giessen, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Nippert
authors.affiliation: Institute of Physiology, Justus-Liebig-University, Giessen, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Schreckenberg
authors.affiliation: Institute of Physiology, Justus-Liebig-University, Giessen, Germany.
authors.forename: Antonia
authors.initials: A
authors.lastname: Hess
authors.affiliation: Institute of Physiology, Justus-Liebig-University, Giessen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Weber
authors.affiliation: Institute of Physiology, Justus-Liebig-University, Giessen, Germany.
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Schlüter
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D002478:Cells, Cultured; D003470:Culture Media; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D008840:Microfilament Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D002135:Calcium-Binding Proteins; D003470:Culture Media; C000621175:Efhd2 protein, rat; D008840:Microfilament Proteins; D034741:RNA, Small Interfering; D011943:Receptors, Adrenergic, beta; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; C496569:Grk2 protein, rat; D054769:G-Protein-Coupled Receptor Kinase 2; D002118:Calcium