Mitofusin-mediated contacts between mitochondria and peroxisomes regulate mitochondrial fusion.

Mitofusins are large GTPases that trigger fusion of mitochondrial outer membranes. Similarly to the human mitofusin Mfn2, which also tethers mitochondria to the endoplasmic reticulum (ER), the yeast mitofusin Fzo1 stimulates contacts between Peroxisomes and Mitochondria when overexpressed. Yet, the physiological significance and function of these "PerMit" contacts remain unknown.

A lipid hydrolase and a ubiquitin ligase play hide-and-seek in the ER membrane.

Complex metabolic diseases such as diabetes and non-alcoholic fatty liver disease have been associated with aberrant lipid metabolism and lipotoxicity. To maintain lipid homeostasis and escape lipotoxicity, cells deploy a plethora of mechanisms, the most fascinating of which relying on a sense-and-response circuit. New work by Volkmar et al reveals an auto-regulated pathway formed by a lipid hydrolase and a lipid-sensitive E3 ubiquitin ligase playing hide-and-seek to warrant membrane function in stressed cells.

The regulation of mitochondrial homeostasis by the ubiquitin proteasome system.

From mitochondrial quality control pathways to the regulation of specific functions, the Ubiquitin Proteasome System (UPS) could be compared to a Swiss knife without which mitochondria could not maintain its integrity in the cell. Here, we review the mechanisms that the UPS employs to regulate mitochondrial function and efficiency. For this purpose, we depict how Ubiquitin and the Proteasome participate in diverse quality control pathways that safeguard entry into the mitochondrial compartment.