The inner and outer compartments of mitochondria are sites of distinct cAMP/PKA signaling dynamics

Abstract

FRET-based sensors for cAMP and PKA activity reveal that mitochondrial subcompartments host segregated cAMP cascades with distinct functional and kinetic signatures.

CO2/HCO3−- and Calcium-regulated Soluble Adenylyl Cyclase as a Physiological ATP Sensor

“…Interestingly, the ATP levels in the sAC-overexpressing cell lines were elevated relative to those in the parental HEK293 cells (Fig. 3A); this could reflect a contribution from increased expression of intramitochondrial sAC, which has been shown to stimulate ATP production (23)(24)(25)(26).…”

“…In addition to its millimolar K m for substrate ATP, in vitro sAC activity is inhibited when ATP levels are very high (4); thus, sAC might serve as an ATP sensor, allowing certain pathways to proceed only when ATP levels are at an optimal level. Also, because intramitochondrial sAC regulates the electron transport chain (23)(24)(25)(26), sAC represents an ATP sensor that can regulate ATP generation. With this study, sAC has now been shown to sense metabolism inside cells via three physiological signals: CO 2 /HCO 3 Ϫ (24, 34), Ca 2ϩ (9,25), and ATP.…”

Calcium-dependent mitochondrial cAMP production enhances aldosterone secretion

“…Intramitochondrial cAMP rise is paralleled by a significant increase of the matrix level of ATP. On the contrary, no consensus exists as to the target(s) of cAMP in the mitochondrial matrix (see for example (Acin-Perez et al, 2009b;Di Benedetto et al, 2013;Lefkimmiatis et al, 2013)). Moreover, and most importantly, the possible functional effects of this cAMP increase are still largely unexplored.…”

“…Despite these contradictions on the relationships between angiotensin II stimulation and cAMP levels, a consensus exists on the synergic actions of cytosolic cAMP produced by ACTH and Ca 2+ rises on aldosterone production (Spät and Hunyady, 2004 suggests that, similarly to what occurring for the cysosolic compartment, the mt-cAMP rise synergizes with intramitochondrial Ca 2+ in regulating aldosterone biosynthesis. The specific molecular target of mt-cAMP, however, remains to be established (Lefkimmiatis et al, 2013).…”

EPAC1 activation by cAMP stabilizes CFTR at the membrane by promoting its interaction with NHERF1

“…The following constructs were used: GFP-EPAC1, GFP-Δ49-EPAC1 and GFP-Δ148-EPAC1, with EPAC1 lacking the first 49 or 148 amino acids, as indicated ; GFP-NHERF1 (NHERF1 tagged at the N-terminus), NHERF1-GFP (NHERF1 tagged at the C-terminus), Myc-NHERF1, GFP-PDZ2-ERM (lacks PDZ1 domain), GFP-ERM (lacking both the PDZ1 and PDZ2 domains) (Castellani et al, 2012;Loureiro et al, 2015); Raichu sensor (Nakamura et al, 2006), with the Rap1 sequence between YFP and CFP; pGEX-RalGDS-RBDGST plasmid (Franke et al, 1997); mCherry and PKI-mCherry (Lefkimmiatis et al, 2013).…”