Calcium release from the Golgi apparatus and the endoplasmic reticulum in HeLa cells stably expressing targeted aequorin to these compartments.
Extracellular agonists mobilize Ca2+ from SERCA-comprising intracellular Ca2+ stores located in both the Golgi apparatus and the endoplasmic reticulum. Ca2+ release from both these compartments was studied in HeLa cells stably expressing the luminescent Ca2+ indicator aequorin specifically targeted to these compartments. Changes in lumenal [Ca2+] as detected by the aequorin measurements were correlated with parallel changes in total Ca2+ content of the stores. The latencies and initial rates of Ca2+ release from the Golgi apparatus and the endoplasmic reticulum were quite similar. However, maximal Ca2+ release measured with Golgi-targeted aequorin terminated faster than that from the endoplasmic reticulum. The rate and extent of Ca2+ depletion from both compartments correlated well with the peak amplitude of the cytosolic [Ca2+] rise. Time-course experiments further revealed that the peak of the cytosolic Ca2+ response occurred before the lumenal [Ca2+] reached its lowest level. We conclude that both the Golgi apparatus and the endoplasmic reticulum contribute to the rise in cytosolic [Ca2+] upon agonist stimulation, but the kinetics of the Ca2+ release are different.
Missiaen
L
L
Afdeling Fysiologie, K.U. Leuven Campus Gasthuisberg O/N, Herestraat 49, B-3000 Leuven, Belgium. ludwig.missiaen@med.kuleuven.ac.be
Van Acker
K
K
Van Baelen
K
K
Raeymaekers
L
L
Wuytack
F
F
Parys
J B
JB
De Smedt
H
H
Vanoevelen
J
J
Dode
L
L
Rizzuto
R
R
Callewaert
G
G
D000331:Aequorin / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology
D000331:Aequorin; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium