SPG7 targets the m-AAA protease complex to process MCU for uniporter assembly, Ca2 influx, and regulation of mitochondrial permeability transition pore opening

The mitochondrial matrix ATPase associated with diverse cellular activities (m-AAA) protease spastic paraplegia 7 (SPG7) has been recently implicated as either a negative or positive regulatory component of the mitochondrial permeability transition pore (mPTP) by two research groups. To address this controversy, we investigated possible mechanisms that explain the discrepancies between these two studies. We found that loss of the SPG7 gene increased resistance to Ca2-induced mPTP opening. However, this occurs independently of cyclophilin D (cyclosporine A insensitive) rather it is through decreased mitochondrial Ca2 concentrations and subsequent adaptations mediated by impaired formation of functional mitochondrial Ca2 uniporter complexes. We found that SPG7 directs the m-AAA complex to favor association with the mitochondrial Ca2 uniporter (MCU) and MCU processing regulates higher order MCU-complex formation. The results suggest that SPG7 does not constitute a core component of the mPTP but can modulate mPTP through regulation of the basal mitochondrial Ca2 concentration

AT1 receptor signaling pathways in the cardiovascular system

The importance of the renin angiotensin aldosterone system in cardiovascular physiology and pathophysiology has been well described whereas the detailed molecular mechanisms remain elusive. The angiotensin II type 1 receptor (AT1 receptor) is one of the key players in the renin angiotensin aldosterone system. The AT1 receptor promotes various intracellular signaling pathways resulting in hypertension, endothelial dysfunction, vascular remodeling and end organ damage. Accumulating evidence shows the complex picture of AT1 receptor-mediated signaling; AT1 receptor-mediated heterotrimeric G protein-dependent signaling, transactivation of growth factor receptors, NADPH oxidase and ROS signaling, G protein-independent signaling, including the β-arrestin signals and interaction with several AT1 receptor interacting proteins. In addition, there is functional cross-talk between the AT1 receptor signaling pathway and other signaling pathways. In this review, we will summarize an up to date overview of essential AT1 receptor signaling events and their functional significances in the cardiovascular system

Pyk2 Expression and Localization in Cardiac Mitochondria and Its Role in Mitochondrial Calcium Regulation

TRPM2 is a non-selective cation channel located in the plasma membrane of the cell. Upon activation, the channel opens, allowing calcium to enter into the cytosol of the cell, leading ultimately to the phosphorylation and activation of the enzyme Pyk2 (proline-rich tyrosine kinase 2). Once phosphorylated, Pyk2 translocates from the cytosol to the mitochondria, where it regulates the formation of the pore component of the mitochondrial calcium uniporter (MCU) complex. Consequently, this interaction is a key factor in mitochondrial calcium uptake and therefore mitochondrial bioenergetics.https://jdc.jefferson.edu/transmedposters/1001/thumbnail.jp