AMPK regulates chromatin dynamics and structure through LaminA

AMP-activated protein kinase (AMPK) is a sensor which regulates cellular energy status. It regulates transcriptional programs that are needed to survive metabolic and environmental stresses by directly associating with chromatin. However, regulation of AMPK and its effects on chromatin dynamics and structure remains unknown. Here, by combining single-nucleosome tracking and super-resolution imaging technique known as direct stochastic optical reconstruction microscopy (dSTORM), we studied the effect of AMPK regulation on chromatin dynamics and higher-order structures in the nucleus of U2OS mammalian cells. We found that inhibition of AMPK causes a reduction in nucleosome dynamics on live cells and reduction in nucleosome clustering in fixed cells. The opposite holds true upon activation of AMPK. We made time course measurements within one hour upon inhibition and observed chromatin dynamics reducing over time. This was also verified with a FRET-based AMPK activity monitor which showed an increase in lifetime upon AMPK inhibition. These observations indicate that AMPK regulation takes place in a diffusion dependent manner. To understand the pathway of AMPK regulation we silenced certain key proteins: SUN2 being part of the trans-luminal linker of nucleoskeleton and cytoskeleton (LINC) complex and LaminA which connects the LINC complex to chromatin in the nucleus. Silencing SUN2 showed no contribution to AMPK regulation, but silencing LaminA did. These findings suggest that AMPK influences chromatin via the nucleus envelope.