Loading neurons with BAPTA-AM activates xbp1 processing indicative of induction of endoplasmic reticulum stress.
Loading cells with the calcium chelator BAPTA-AM is an analytical tool which has been used to suppress a rise in cytoplasmic calcium activity under various experimental conditions and thus, to evaluate the role of elevated cytoplasmic calcium levels in the process under investigation. BAPTA-AM may, however, not only have an isolated effect on cytoplasmic processes but also on functions of other subcellular compartments such as the endoplasmic reticulum (ER). Under conditions associated with ER dysfunction, the unfolded protein response is activated which is characterized by suppression of translation and processing of xbp1 mRNA, resulting in activation of the expression of genes coding for ER stress proteins. To investigate whether BAPTA-AM causes ER stress, primary neuronal cell cultures were loaded with varying amounts of BAPTA-AM. Exposure of cells to BAPTA-AM induced a marked rise in processed xbp1 mRNA levels, correlating with exposure times and BAPTA-AM concentrations in the medium used for loading. The increase in processed xbp1 mRNA was associated with suppression of protein synthesis and induction of cell injury. The results of this study indicate that loading primary neuronal cell cultures with BAPTA-AM activates xbp1 processing, implying that this calcium chelator does not have an isolated effect on cytoplasmic calcium activity but also an affect on ER function.
Paschen
Wulf
W
Department of Experimental Neurology, Max-Planck-Institute for Neurological Research, Gleuelerstr 50, Cologne 50931, Köln, Germany. paschen@mpin.mphg.de
Hotop
Svenja
S
Aufenberg
Christoph
C
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000037:antagonists & inhibitors / Q000172:deficiency*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D018388:Codon, Terminator / Q000502:physiology; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D005333:Fetus; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006706:Homeostasis / Q000187:drug effects / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D017510:Protein Folding; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000071701:Regulatory Factor X Transcription Factors; D013312:Stress, Physiological / Q000378:metabolism*; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D000071717:X-Box Binding Protein 1
D002614:Chelating Agents; D018388:Codon, Terminator; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605545:Xbp1 protein, rat; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D002118:Calcium