AMPK-dependent phosphorylation of MTFR1L regulates mitochondrial morphology

Abstract

Mitochondria are dynamic organelles that undergo membrane remodeling events in response to metabolic alterations to generate an adequate mitochondrial network. Here, we investigated the function of mitochondrial fission regulator 1-like protein (MTFR1L), an uncharacterized protein that has been identified in phosphoproteomic screens as a potential AMP-activated protein kinase (AMPK) substrate. We showed that MTFR1L is an outer mitochondrial membrane–localized protein modulating mitochondrial morphology. Loss of MTFR1L led to mitochondrial elongation associated with increased mitochondrial fusion events and levels of the mitochondrial fusion protein, optic atrophy 1. Mechanistically, we show that MTFR1L is phosphorylated by AMPK, which thereby controls the function of MTFR1L in regulating mitochondrial morphology both in mammalian cell lines and in murine cortical neurons in vivo. Furthermore, we demonstrate that MTFR1L is required for stress-induced AMPK-dependent mitochondrial fragmentation. Together, these findings identify MTFR1L as a critical mitochondrial protein transducing AMPK-dependent metabolic changes through regulation of mitochondrial dynamics.

Activity-dependent subcellular compartmentalization of dendritic mitochondria structure in CA1 pyramidal neurons

“…Collectively, our results (summarized in Fig. 7) demonstrate that the mitochondrial morphology observed in the SR and SO dendritic compartments is shaped by synaptic activity via Camkk2dependent AMPK phosphorylation of the pro-fission Drp1 receptor Mff 11,23 and phosphorylation of the antifusion Mtfr1l 33 , a protein antagonizing Opa1.…”

“…Previous results identified two direct effectors phosphorylated by AMPK mediating mitochondrial fission: the Drp1-receptor Mff 23 and the anti-fusion, Opa1-inhibiting protein Mitochondrial Fission Regulator 1-Like (Mtfr1l) 33 . We performed CA1-targeted IUE with cytoplasmic fluorescent proteins (tdTomato, mGreenLantern) and mitochondrial matrix-targeted fluorescent proteins (mt-YFP, mt-DsRed) in combination with either a control, non-targeting shRNA (shNT) or an shRNA targeting Mtfr1l ( Fig.…”

“…For excitation, we used a Chameleon, Ultra II (Coherent) laser tuned to 920 nm. We continuously acquired red (tdTomato) and green (GCaMP6f) channels separated by an emission cube set (green: HQ525/70 m-2p; red: HQ607/45 m-2p; constitutive knockout mice were IUE with the same mitochondrial markers/cell fills as in Figure 3 (WT and Camkk2 -/-) and a plasmid cDNA expressing phosphomimetic mutant on the two serine residues phosphorylated by AMPK (S103D and S238D) of Mtfr1l (Mtfr1l S2D ) 33 . Data and quantifications from WT and Camkk2 -/are the same as in Figure 3.…”

Calcium signals tune AMPK activity and mitochondrial homeostasis in dendrites of developing neurons

“…fission regulator 1-like protein (MTFR1L) [16][17][18][19][20][21][22] . AMPK is activated by direct allosteric binding of AMP, facilitating phosphorylation at Thr172 by an upstream kinase LKB1 in response to cellular ATP shortage 23 .…”

“…Recent studies have highlighted the role of AMP-activated protein kinase (AMPK) as an energy sensor that sustains the metabolic state by regulating mitochondrial dynamics and functions 18 . AMPK regulates several aspects of mitochondrial homeostasis by direct phosphorylation of key factors, including MFF, peroxisome proliferator-activated receptor-coactivator 1 (PGC1α), Armadillo repeat-containing protein 10 (ARMC10), Unc-51 like autophagy activating kinases 1 and 2 (ULK1/2) and Mitochondrial fission regulator 1-like protein (MTFR1L) [19][20][21][22][23][24][25] . AMPK is activated by direct allosteric binding of AMP, facilitating phosphorylation at Thr172 by an upstream kinase LKB1 in response to cellular ATP shortage 26 .…”