Endoplasmic reticulum Ca(2+) content decrease by PKA-dependent hyperphosphorylation of type 1 IP3 receptor contributes to prostate cancer cell resistance to androgen deprivation.
Reference treatment of advanced prostate cancer (PCa) relies on pharmacological or surgical androgen deprivation therapy. However, it is only temporarily efficient as tumor cells inevitably adapt to the low testosterone environment and become hormone-refractory (HRPCa). We observed that androgen removal in HRPCa-derived LNCaP cells causes different alterations in their Ca(2+) homeostasis among which a reduction of ER Ca(2+) content. We show that the decrease in [Ca(2+)]ER is due to a modest overexpression of type 1 IP3R and a threefold increased phosphorylation of IP3R1 on Ser-1716, a protein kinase A (PKA) consensus site, both implicated in ER Ca(2+) leak. Accordingly, ER Ca(2+) content was restored by siRNA-mediated down-regulation of IP3R1 or by inhibition of its phosphorylation by competition with a permeant TAT-peptide containing the Ser-1716 consensus phosphorylation sequence or by treatment with the PKA inhibitor H89. Moreover, inhibition of the IP3R1 phosphorylation by both methods sensitized the LNCaP cells to androgen deprivation-induced apoptosis. In addition, SERCA2b overexpression precluded the effect of androgen deprivation on ER Ca(2+) store content and reduced resistance to androgen deprivation. Taken together, these results indicate that lowering the ER Ca(2+)-store content by increasing IP3R1 levels and IP3R1 phosphorylation by PKA is a protective mechanism by which HRPCa-derived cells escape cell death in the absence of androgenic stimulation.
Laboratory of Cell Physiology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium.
Benoît
B
Boutin
Laboratory of Cell Physiology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium.
Nicolas
N
Tajeddine
Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium.
Giovanni
G
Monaco
CNRS, Institut de Neurobiologie Alfred Fessard, Laboratoire de Neurobiologie et Développement, UPR 3294, 1 Avenue de la Terrasse, bâtiments 32-33, 91198 Gif sur Yvette Cedex, France.
Jordi
J
Molgo
de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
Didier
D
Vertommen
de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
Mark
M
Rider
Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium.
Jan B
JB
Parys
Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium.
Geert
G
Bultynck
Laboratory of Cell Physiology, Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium. Electronic address: philippe.gailly@uclouvain.be.
Philippe
P
Gailly
D000728:Androgens / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism*; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000188:drug therapy*; D034741:RNA, Small Interfering / Q000235:genetics; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D013739:Testosterone / Q000378:metabolism; D019076:Transgenes / Q000235:genetics; D019139:Tumor Escape
D000728:Androgens; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007546:Isoquinolines; D010446:Peptide Fragments; D034741:RNA, Small Interfering; D013449:Sulfonamides; D013739:Testosterone; D017868:Cyclic AMP-Dependent Protein Kinases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506946:ATP2A2 protein, human; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium
Apoptosis; Endoplasmic reticulum; Hormone therapy; IP3R1; PKA; Prostate cancer