title: Sumoylation regulates nuclear localization of lipin-1alpha in neuronal cells.
abstract: Lipin-1 is a protein that has dual functions as a phosphatidic acid phosphohydrolase (PAP) and a nuclear transcriptional coactivator. It remains unknown how the nuclear localization and coactivator functions of lipin-1 are regulated. Here, we show that lipin-1 (including both the alpha and beta isoforms) is modified by sumoylation at two consensus sumoylation sites. We are unable to detect sumoylation of the related proteins lipin-2 and lipin-3. Lipin-1 is sumoylated at relatively high levels in brain, where lipin-1alpha is the predominant form. In cultured embryonic cortical neurons and SH-SY5Y neuronal cells, ectopically expressed lipin-1alpha is localized in both the nucleus and the cytoplasm, and the nuclear localization is abrogated by mutating the consensus sumyolation motifs. The sumoylation site mutant of lipin-1alpha loses the capacity to coactivate the transcriptional (co-) activators PGC-1alpha and MEF2, consistent with its nuclear exclusion. Thus, these results show that sumoylation facilitates the nuclear localization and transcriptional coactivator behavior of lipin-1alpha that we observe in cultured neuronal cells, and suggest that lipin-1alpha may act as a sumoylation-regulated transcriptional coactivator in brain.
authors.affiliation: Department of Cell Biology, The Scripps Research Institute, La Jolla, California, USA. ghliu@scripps.edu
authors.forename: Guang-Hui
authors.initials: GH
authors.lastname: Liu
authors.forename: Larry
authors.initials: L
authors.lastname: Gerace
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001921:Brain / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008856:Microscopy, Fluorescence / Q000379:methods; D009474:Neurons / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010711:Phosphatidate Phosphatase; D025842:SUMO-1 Protein / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D009687:Nuclear Proteins; D025842:SUMO-1 Protein; C495501:SUMO1 protein, human; C485999:LPIN1 protein, human; C418978:Lpin1 protein, mouse; D010711:Phosphatidate Phosphatase