AUTHOR=Kamran Hamza , Lee Jung Kwon , Lee Ki-Young 

TITLE=PKA inhibition is a central step in D,L-methadone-induced ER Ca2+ release and subsequent apoptosis in acute lymphoblastic leukemia

JOURNAL=Frontiers in Cell and Developmental Biology

VOLUME=Volume 12 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2024.1388745

DOI=10.3389/fcell.2024.1388745

ISSN=2296-634X

ABSTRACT=Acute lymphoblastic leukemia (ALL) is a hematologic cancer that mostly affects children. It accounts for over a quarter of ALL pediatric cancers, causing most of the cancer death among children. Previously, we demonstrated that D,L-methadone causes ALL cell apoptosis via -opioid receptor 1 (OPRM1)triggered ER Ca 2+ release and decrease in Ca 2+ efflux, elevating [Ca 2+ ]i. However, the precise mechanism by which D,L-methadone induces ER Ca 2+ release remains to be defined. Here, we show that in ALL cells, D,L-methadone-induced ER Ca 2+ release is blocked by inhibition of Gαi, but not Gϒ, indicating that the process is dependent on Gαi. Activation of adenylate cyclase (AC) with forskolin or treatment with 8-CPT-cAMP blocks D,L-methadone-induced ER Ca 2+ release, indicating that the latter results from Gαidependent downregulation of AC and cAMP. The 14-22 amide (myr) PKA inhibitor alone elicits ER Ca 2+ release, and subsequent treatment with D,L-methadone does not cause additional ER Ca 2+ release, indicating that PKA inhibition is a key step in D,L-methadone-induced ER Ca 2+ release and can bypass the D,L-methadone-OPRM1-AC-cAMP step. This is consistent with the decrease in PKA-dependent (i) inhibitory PLC3 Ser1105 phosphorylation that leads to PLC3 activation and ER Ca 2+ release, and (ii) BAD Ser118 phosphorylation, which together ultimately result in caspase activation and apoptosis. Thus, our findings indicate that D,L-methadone-induced ER Ca 2+ release and subsequent apoptosis in ALL cells is mediated by Gαi-dependent downregulation of the AC-cAMP-PKA-PLC3/BAD pathway. The fact that 14-22 amide (myr) alone effectively kills ALL cells suggests that PKA may be targeted for ALL therapy.