ABSTRACT
Phosphatase and tensin homolog (PTEN) is a multifunctional gene involved in a variety of physiological and pathological processes. Circular RNAs (circRNAs) are generated from back-splicing events during mRNA processing and participate in cell biological processes through binding to RNAs or proteins. However, PTEN-related circRNAs are largely unknown. Here, we report that circPTEN- mitochondria (MT) (hsa_circ_0002934) is a circular RNA encoded by exons 3, 4, and 5 of PTEN and is a critical regulator of mitochondrial energy metabolism. CircPTEN-MT is localized to mitochondria and physically associated with leucine-rich pentatricopeptide repeat-containing protein (LRPPRC), which regulates posttranscriptional gene expression in mitochondria. Knocking down circPTEN-MT reduces the interaction of LRPPRC and steroid receptor RNA activator (SRA) stem-loop interacting RNA binding protein (SLIRP) and inhibits the polyadenylation of mitochondrial mRNA, which decreases the mRNA level of the mitochondrial complex I subunit and reduces mitochondrial membrane potential and adenosine triphosphate production. Our data demonstrate that circPTEN-MT is an important regulator of cellular energy metabolism. This study expands our understanding of the role of PTEN, which produces both linear and circular RNAs with different and independent functions.
Subject(s)
Energy Metabolism , Mitochondria , PTEN Phosphohydrolase , RNA, Circular , RNA-Binding Proteins , PTEN Phosphohydrolase/genetics , PTEN Phosphohydrolase/metabolism , RNA, Circular/genetics , RNA, Circular/metabolism , Humans , Mitochondria/genetics , Mitochondria/metabolism , Energy Metabolism/genetics , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Membrane Potential, Mitochondrial/genetics , Electron Transport Complex I/genetics , Electron Transport Complex I/metabolism , Adenosine Triphosphate/metabolism , HEK293 Cells , Neoplasm ProteinsABSTRACT
PTEN is a critical tumour suppressor that is frequently mutated in human cancer. We have previously identified a CUG initiated PTEN isoform designated PTENα, which functions in mitochondrial bioenergetics. Here we report the identification of another N-terminal extended PTEN isoform, designated PTENß. PTENß translation is initiated from an AUU codon upstream of and in-frame with the AUG initiation sequence for canonical PTEN. We show that the Kozak context and a downstream hairpin structure are critical for this alternative initiation. PTENß localizes predominantly in the nucleolus, and physically associates with and dephosphorylates nucleolin, which is a multifunctional nucleolar phosphoprotein. Disruption of PTENß alters rDNA transcription and promotes ribosomal biogenesis, and this effect can be reversed by re-introduction of PTENß. Our data show that PTENß regulates pre-rRNA synthesis and cellular proliferation. These results demonstrate the complexity of the PTEN protein family and the diversity of its functions.
Subject(s)
DNA, Ribosomal/genetics , PTEN Phosphohydrolase/genetics , Protein Biosynthesis/genetics , Transcription, Genetic , Alternative Splicing , Animals , Cell Line, Tumor , Cell Nucleolus/genetics , Cell Nucleolus/metabolism , Codon, Initiator/genetics , HCT116 Cells , HEK293 Cells , HeLa Cells , Hep G2 Cells , Humans , Mice, Inbred C57BL , Phosphoproteins/genetics , Phosphoproteins/metabolism , Phosphorylation , Protein Isoforms/genetics , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , NucleolinABSTRACT
OBJECTIVE: To study whether there is apoptosis in brainstem neurons while aging by oberving the distribution of Caspase-3 positive apoptotic cells in in brainstem of young and old SD rats. METHODS: Healthy male SD rats were divided into 2 groups (3 and 18 month-old respectively), 3 rats each group. Brainstem specimens were treated followed the brainstem's common paraffin embedding, sectioning and HE staining procedures (sections were 6 µm in thickness). The sections were also determined by Caspase-3 immunostaining and TUNEL. The Caspase-3 positive cells on the rat stereotaxic atlas were drew, then composed the sections into a 3D model. RESULTS: Compared to 3 month-old rats, there were more Caspase-3 positive neurons in the brainstem and the positive neurons were distributed more extensively in 18 month-old rats spectially in nucleus of solitary tract and pontine reticular nuclei. CONCLUSION: More neurons suffer apoptotic changes in the brainstem while aging.
