Dear Editor,

Protein phosphorylation is essential for multiple cellular processes. This post-translational modification is regulated by kinase-mediated phosphorylation and phosphatase-mediated dephosphorylation. Drosophila protein phosphatase V (PpV) and Saccharomyces cerevisiae Sit4 are homologs of mammalian PP6, which belongs to the PP2A subfamily of serine/threonine phosphatases (Mann et al., 1993; Wang et al., 2012). In addition to the catalytic subunit, PP6 holoenzyme also contains a regulatory subunit (PP6R1, PP6R2, or PP6R3 in human; Sap4, Sap155, Sap185, or Sap190 in yeast; CG10289 in fly) and a scaffold subunit (Morales-Johansson et al., 2009). Studies in S. cerevisiae showed that Sit4 knockout strain had reduced lipid droplet content and increased phosphorylation of SNF1 (a homolog of mammalian and Drosophila AMPK) at an evolutionally conserved activation site (Bozaquel-Morais et al., 2010; Ruiz et al., 2011). However, its function in metazoan has not been well explored.