title: Binding of the stress protein alpha B-crystallin to cardiac myofibrils correlates with the degree of myocardial damage during ischemia/reperfusion in vivo.
abstract: Stress proteins are assumed to protect cells against various kinds of stresses including ischemia. In this study, we focused on the behaviour of the most abundant myocardial stress protein, alpha B-crystallin, during ischemia and reperfusion of the pig heart in vivo, alpha B-crystallin constitutes 1-2% of the soluble protein pool and underwent, during severe but reversibly damaging ischemia (25 min), complete translocation to the Z-line area of myofibrils. Irreversibly damaging ischemia (60 min) was accompanied by extreme stretching of the majority of myofibrils, and by concomitant extension of alpha B-crystallin localization from the Z-line area to I-bands. This I-band shift correlated with displacement of the T12 epitope of titin from the vicinity of Z-lines into I-bands, indicating that the primary binding sites for alpha B-crystallin might also be located in juxtaposition to Z-lines and move into the I-bands during extreme sarcomeric stretching. During reperfusion after 25 min of ischemia, alpha B-crystallin disappeared rapidly from myofibrils: whereas reperfusion after irreversibly damaging ischemia (60 min) resulted in dissociation of alpha B-crystallin only from those myofibrils and myocardiocytes that were still able to contract, and alpha B-crystallin remained bound to the overstretched, damaged myofibrils no longer capable of contraction. The time course of translocation of alpha B-crystallin to myofibrils during ischemia correlated with phosphorylation of approximately 20% of the entire alpha B-crystallin pool. However, disappearance of alpha B-crystallin from myofibrils during reperfusion was not accompanied by dephosphorylation, indicating that phosphorylation alone does not explain myofibrillar binding of alpha B-crystallin. Ischemia-induced myofibrillar targeting of alpha B-crystallin probably requires additional structural and posttranslational modifications of myofibrillar components in juxtaposition to I-bands.
authors: Institute of Anatomy, Julius-Maximilians-University, Würzburg, Germany.
authors: N
authors: N
authors: Golenhofen
authors: P
authors: P
authors: Htun
authors: W
authors: W
authors: Ness
authors: R
authors: R
authors: Koob
authors: W
authors: W
authors: Schaper
authors: D
authors: D
authors: Drenckhahn
mesh_terms: D000185:Actinin / Q000378:metabolism; D000818:Animals; D064211:Connectin; D003459:Crystallins / Q000378:metabolism* / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D015151:Immunoblotting; D007908:Lens, Crystalline / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron; D009124:Muscle Proteins / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism / Q000648:ultrastructure; D009210:Myofibrils / Q000378:metabolism* / Q000648:ultrastructure; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D015427:Reperfusion Injury / Q000378:metabolism*; D012518:Sarcomeres / Q000378:metabolism; D013552:Swine; D013997:Time Factors
chemical_list: D064211:Connectin; D003459:Crystallins; D009124:Muscle Proteins; D000185:Actinin; D011494:Protein Kinases