Mitochondrial Ca2+ uptake is inhibited by a concerted action of p38 MAPK and protein kinase D

Area of Science:

• Cellular Biology
• Biochemistry
• Physiology

Background:

• Angiotensin II triggers cytosolic calcium signals transferred to mitochondria.
• Previous studies identified p38 MAPK and novel PKC involvement in enhancing mitochondrial calcium uptake.
• The precise mechanisms controlling mitochondrial calcium handling remain under investigation.

Purpose of the Study:

• To investigate the role of simultaneous activation of p38 MAPK, novel PKC, and protein kinase D (PKD) in regulating mitochondrial calcium uptake.
• To determine if these kinases modulate the transfer of cytosolic calcium signals into mitochondria.
• To elucidate the impact of kinase activity on preventing mitochondrial calcium overload.

Main Methods:

• Utilized H295R cells for experiments.
• Activated protein kinases using TNFalpha and PMA with conventional PKC inhibitors.
• Assessed cytosolic and mitochondrial calcium signals following depolarization or store-operated calcium influx.
• Employed p38 MAPK inhibitor SB202190 and gene silencing of PKD.

Main Results:

• Simultaneous activation of p38 MAPK, novel PKC, and PKD attenuated cytosolic calcium signal transfer to mitochondria.
• The inhibitory effect of SB202190 on p38 MAPK enhanced mitochondrial calcium uptake, confirming kinase-dependent action.
• Protein kinases were found to inhibit mitochondrial calcium uptake mechanisms.
• PKD silencing also led to enhanced cytosolic-to-mitochondrial calcium signal transfer.
• Mitochondrial calcium uptake threshold appears dependent on p38 MAPK activity.

Conclusions:

• Ca2+ mobilizing agonists activate p38 MAPK, novel PKC, and PKD simultaneously.
• This activation results in a negative feedback mechanism on mitochondrial calcium uptake.
• This coordinated kinase activity serves to reduce the risk of mitochondrial calcium overload.