AMPK governs lineage specification through Tfeb-dependent regulation of lysosomes

Abstract

Faithful execution of developmental programs relies on the acquisition of unique cell identities from pluripotent progenitors, a process governed by combinatorial inputs from numerous signaling cascades that ultimately dictate lineage-specific transcriptional outputs. Despite growing evidence that metabolism is integrated with many molecular networks, how pathways that control energy homeostasis may affect cell fate decisions is largely unknown. Here, we show that AMP-activated protein kinase (AMPK), a central metabolic regulator, plays critical roles in lineage specification. Although AMPK-deficient embryonic stem cells (ESCs) were normal in the pluripotent state, these cells displayed profound defects upon differentiation, failing to generate chimeric embryos and preferentially adopting an ectodermal fate at the expense of the endoderm during embryoid body (EB) formation. AMPK −/− EBs exhibited reduced levels of Tfeb, a master transcriptional regulator of lysosomes, leading to diminished endolysosomal function. Remarkably, genetic loss of Tfeb also yielded endodermal defects, while AMPK-null ESCs overexpressing this transcription factor normalized their differential potential, revealing an intimate connection between Tfeb/lysosomes and germ layer specification. The compromised endolysosomal system resulting from AMPK or Tfeb inactivation blunted Wnt signaling, while up-regulating this pathway restored expression of endodermal markers. Collectively, these results uncover the AMPK pathway as a novel regulator of cell fate determination during differentiation.

Acute and chronic mitochondrial respiratory chain deficiency differentially regulate lysosomal biogenesis

“…We next tested if activation of AMPK, in the absence of mitochondrial stress, was enough to trigger TFEB-dependent transcription. For this we treated HeLa cells with A769662, a commonly used AMPK activator24, for 4-hours and determined the transcript levels of lysosomal genes. No significant increase was observed (Fig.…”

TFEB at a glance

“…Furthermore, TFEB activity has been associated with dendritic cell maturation (Samie and Cresswell, 2015) and osteoclast differentiation (Ferron et al, 2013). TFEB depletion in ESCs has been associated with defective differentiation into the endodermal lineage (Young et al, 2016). These defects appear to be caused by an impaired ability of TFEBdeficient ESCs to induce the canonical Wnt signaling; this is thought to be due to the lack of a fully functional lysosomal compartment (Young et al, 2016), which is required for proper Wnt signaling (Cruciat et al, 2010).…”

“…TFEB depletion in ESCs has been associated with defective differentiation into the endodermal lineage (Young et al, 2016). These defects appear to be caused by an impaired ability of TFEBdeficient ESCs to induce the canonical Wnt signaling; this is thought to be due to the lack of a fully functional lysosomal compartment (Young et al, 2016), which is required for proper Wnt signaling (Cruciat et al, 2010). A functional lysosomal compartment is also required for Notch activation (Vaccari et al, 2010).…”

“…TFEB-null mice die at embryonic day (E)9.5-10.5 because of defective placental vascularization (Steingrimsson et al, 1998). Recent evidence has shown that TFEB governs endodermal specification during embryoid body formation (Young et al, 2016) (see also Box 1).…”

The tumor suppressor FLCN mediates an alternate mTOR pathway to regulate browning of adipose tissue

“…It is possible that the FLCN-AMPK pathway proposed by Yan et al (2016) superimposes on this pathway by modulating mTOR/TFE3. A recent report (Young et al 2016) showed in embryoid bodies that AMPK promotes the activity of TFEB, a molecule highly homologous to TFE3, and that this regulation of TFEB by AMPK occurs at least partly through mTOR. It is therefore possible that AMPK also activates TFE3 in adipose tissue via the same mTOR mechanism.…”