title: Potential role of cardiac calsequestrin in the lethal arrhythmic effects of cocaine.
abstract: BACKGROUND
  Cocaine-related deaths are continuously rising and its overdose is often associated with lethal cardiotoxic effects.
  
  
  RESULTS
  Our approach, employing isothermal titration calorimetry (ITC) and light scattering in parallel, has confirmed the significant affinity of human cardiac calsequestrin (CASQ2) for cocaine. Calsequestrin (CASQ) is a major Ca(2+)-storage protein within the sarcoplasmic reticulum (SR) of both cardiac and skeletal muscles. CASQ acts as a Ca(2+) buffer and Ca(2+)-channel regulator through its unique Ca(2+)-dependent oligomerization. Equilibrium dialysis and atomic absorption spectroscopy experiments illustrated the perturbational effect of cocaine on CASQ2 polymerization, resulting in substantial reduction of its Ca(2+)-binding capacity. We also confirmed the accumulation of cocaine in rat heart tissue and the substantial effects cocaine has on cultured C2C12 cells. The same experiments were performed with methamphetamine as a control, which displayed neither affinity for CASQ2 nor any significant effects on its function. Since cocaine did not have any direct effect on the Ca(2+)-release channel judging from our single channel recordings, these studies provide new insights into how cocaine may interfere with the normal E-C coupling mechanism with lethal arrhythmogenic consequences.
  
  
  CONCLUSIONS
  We propose that cocaine accumulates in SR through its affinity for CASQ2 and affects both SR Ca(2+) storage and release by altering the normal CASQ2 Ca(2+)-dependent polymerization. By this mechanism, cocaine use could produce serious cardiac problems, especially in people who have genetically-impaired CASQ2, defects in other E-C coupling components, or compromised cocaine metabolism and clearance.
authors.affiliation: School of Molecular Biosciences, Washington State University, Pullman, WA 99164, United States.
authors.forename: Emiliano J
authors.initials: EJ
authors.lastname: Sanchez
authors.forename: Robert P
authors.initials: RP
authors.lastname: Hayes
authors.forename: John T
authors.initials: JT
authors.lastname: Barr
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Lewis
authors.forename: Brian N
authors.initials: BN
authors.lastname: Webb
authors.forename: Arun K
authors.initials: AK
authors.lastname: Subramanian
authors.forename: Mark S
authors.initials: MS
authors.lastname: Nissen
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Jones
authors.forename: Eric A
authors.initials: EA
authors.lastname: Shelden
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Sorg
authors.forename: Michael
authors.initials: M
authors.lastname: Fill
authors.forename: James O
authors.initials: JO
authors.lastname: Schenk
authors.forename: Chulhee
authors.initials: C
authors.lastname: Kang
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced* / Q000503:physiopathology; D015220:Calcium Channels / Q000502:physiology; D002151:Calorimetry; D002155:Calsequestrin / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D003042:Cocaine / Q000009:adverse effects* / Q000378:metabolism; D003956:Dialysis; D006321:Heart / Q000503:physiopathology*; D008027:Light; D051379:Mice; D008958:Models, Molecular; D008970:Molecular Weight; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D012542:Scattering, Radiation; D013054:Spectrophotometry, Atomic
chemical_list: D015220:Calcium Channels; D002155:Calsequestrin; D003042:Cocaine
keywords: CASQ; CPVT; Calsequestrin; Cocaine; ITC; K(d); Methamphetamine; RYR; Ryanodine receptor; SR; Sarcoplasmic reticulum; calsequestrin; catecholamine-induced polymorphic ventricular tachycardia; dissociation constant; isothermal titration calorimetry; ryanodine receptor; sarcoplasmic reticulum