title: Intracellular two-phase Ca2+ release and apoptosis controlled by TRP-ML1 channel activity in coronary arterial myocytes.
abstract: Activation of the death receptor Fas has been reported to produce a two-phase intracellular Ca(2+) release response in coronary arterial myocytes (CAMs), which consists of local Ca(2+) bursts via lysosomal transient potential receptor-mucolipin 1 (TRP-ML1) channels and consequent Ca(2+) release from the sarcoplasmic reticulum (SR). The present study was designed to explore the molecular mechanism by which lysosomal Ca(2+) bursts are coupled with SR Ca(2+) release in mouse CAMs and to determine the functional relevance of this lysosome-associated two-phase Ca(2+) release to apoptosis, a common action of Fas activation with Fas ligand (FasL). By confocal microscopy, we found that transfection of CAMs with TRP-ML1 small interfering (si)RNA substantially inhibited FasL (10 ng/ml)-induced lysosome Ca(2+) bursts and consequent SR Ca(2+) release. In contrast, transfection of CAMs with plasmids containing a full-length TRP-ML1 gene enhanced FasL-induced two-phase Ca(2+) release. We further demonstrated that FasL significantly increased the colocalization of the lysosomal marker Lamp1 with ryanodine receptor 3 and enhanced a dynamic trafficking of lysosomes to the SR. When CAMs were treated with TRP-ML1 siRNA, FasL-induced interactions between the lysosomes and SR were substantially blocked. Functionally, FasL-induced apoptosis and activation of calpain and calcineurin, the Ca(2+) sensitive proteins that mediate apoptosis, were significantly attenuated by silencing TRP-ML1 gene but enhanced by overexpression of TRP-ML1 gene. These results suggest that TRP-ML1 channel-mediated lysosomal Ca(2+) bursts upon FasL stimulation promote lysosome trafficking and interactions with the SR, leading to apoptosis of CAMs via a Ca(2+)-dependent mechanism.
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Xu
authors.forename: Xiaoxue
authors.initials: X
authors.lastname: Li
authors.forename: Scott W
authors.initials: SW
authors.lastname: Walsh
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Justine M
authors.initials: JM
authors.lastname: Abais
authors.forename: Krishna M
authors.initials: KM
authors.lastname: Boini
authors.forename: Pin-Lan
authors.initials: PL
authors.lastname: Li
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002154:Calpain / Q000378:metabolism; D003331:Coronary Vessels / Q000166:cytology / Q000378:metabolism*; D053222:Fas Ligand Protein / Q000378:metabolism; D005260:Female; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D051379:Mice; D032342:Muscle Cells / Q000166:cytology* / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D050051:Transient Receptor Potential Channels / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D002118:Calcium; D002154:Calpain; D053222:Fas Ligand Protein; D051907:Lysosomal Membrane Proteins; D034741:RNA, Small Interfering; D019837:Ryanodine Receptor Calcium Release Channel; D050051:Transient Receptor Potential Channels; D019014:fas Receptor; C052255:Lamp1 protein, mouse; D052118:Lysosomal-Associated Membrane Protein 1; C512321:Mcoln1 protein, mouse