ULK2 Ser 1027 Phosphorylation by PKA Regulates Its Nuclear Localization Occurring through Karyopherin Beta 2 Recognition of a PY-NLS Motif.

ABSTRACT: Uncoordinated 51-like kinase 2 (ULK2), a member of the serine/threonine kinase family, plays an essential role in the regulation of autophagy in mammalian cells. Given the role of autophagy in normal cellular homeostasis and in multiple diseases, improved mechanistic insight into this process may result in the development of novel therapeutic approaches. Here, we present evidence that ULK2 associates with karyopherin beta 2 (Kap?2) for its transportation into the nucleus. We identify a potential PY-NLS motif ((774)gpgfgssppGaeaapslRyvPY(795)) in the S/P space domain of ULK2, which is similar to the consensus PY-NLS motif (R/K/H)X(2-5)PY. Using a pull-down approach, we observe that ULK2 interacts physically with Kap?2 both in vitro and in vivo. Confocal microscopy confirmed the co-localization of ULK2 and Kap?2. Localization of ULK2 to the nuclear region was disrupted by mutations in the putative Kap?2-binding motif (P794A). Furthermore, in transient transfection assays, the presence of the Kap?2 binding site mutant (the cytoplasmic localization form) was associated with a substantial increase in autophagy activity (but a decrease in the in vitro serine-phosphorylation) compared with the wild type ULK2. Mutational analysis showed that the phosphorylation on the Ser1027 residue of ULK2 by Protein Kinase A (PKA) is the regulatory point for its functional dissociation from Atg13 and FIP 200, nuclear localization, and autophagy. Taken together, our observations indicate that Kap?2 interacts with ULK2 through ULK2's putative PY-NLS motif, and facilitates transport from the cytoplasm to the nucleus, depending on its Ser1027 residue phosphorylation by PKA, thereby reducing autophagic activity.

SUBMITTER: Shin SH 

PROVIDER: S-EPMC4460075 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature