Recombinant Mouse Transmembrane protein 223 (Tmem223)

Introduction

Transmembrane protein 223 (TMEM223) is a protein that interacts with the mitochondrial ribosome and functions in the biogenesis of cytochrome $$c$$ oxidase . It is an integral protein of the inner mitochondrial membrane (IMM) with its N- and C-termini facing the mitochondrial matrix .

3.1. Impact on Cytochrome $$c$$ Oxidase

Knockout studies utilizing CRISPR/Cas9 to target the TMEM223 gene have revealed that loss of TMEM223 results in a reduction of the late assembling complex IV subunit COX6A, while COX4-1 or the COX1 assembly factors C12ORF62 (COX14) and MITRAC12 (COA3) were not altered . Also, proteins of other OXPHOS complexes, such as NDUFA9 (complex I), SDHA (complex II), or ATP5B (complex V), remained unaffected . An increase of RIESKE, a core protein of complex III, has been observed . Cytochrome $$c$$ oxidase activity is reduced to 62.5% of wild-type (WT) in TMEM223−/− cells .

3.2. Role in Mitochondrial Translation

TMEM223 is required for translation of mitochondrial-encoded complex IV subunits . [35S]methionine labeling of mitochondrial translation products revealed a significant decrease in the levels of newly synthesized COX1 in TMEM223−/− cells compared to WT, while other mitochondrial-encoded proteins, including COX2 and COX3, displayed no differences . A comparable reduction of COX1 synthesis to 61.23% was observed using a [35S]methionine labeling approach in siRNA-mediated depleted TMEM223 cells .

3.3. Interactome Analysis

TMEM223 interacts with early .

TMEM223 and Apoptosis

Ectopic expression of wild-type (WT) and Parkinson’s disease (PD)-linked mutant TMEM230 variants in cultured cells dramatically induced apoptotic cell death compared with that of vector control cells . Mutant TMEM230 caused cell toxicity at an increased severity than WT TMEM230 . Expression of TMEM230 increased mitochondrial reactive oxygen species (ROS) levels, decreased cellular ATP, activated caspase 3/7, and increased poly(ADP-ribose) polymerase-1 (PARP1) cleavage . Treatment with N-acetylcysteine (NAC; an ROS scavenger) or Z-VAD-FMK (a caspase inhibitor) significantly attenuated TMEM230-induced apoptosis in both cultured cells and primary neurons . TMEM230 mediates a PARP1-linked apoptotic cell death pathway .

TMEM230 in Angiogenesis and Tumor Therapy

TMEM230 promotes aspects of angiogenesis in parallel or independently of the Delta/Notch and VEGF signaling pathways and has the properties of being a novel master regulator in angiogenesis . Precise regulated levels of TMEM230 expression may determine its role in normal or disease-associated angiogenesis . TMEM230 is expressed in human tumors and may represent a promising novel drug target for antiangiogenic or antitumor therapy to restrict GBM tumor cell properties and tumor cell-promoted angiogenesis .