Transmembrane Protein 230 Research Articles

Mutant-TMEM230-induced neurodegeneration and impaired axonal mitochondrial transport.

Parkinson's disease (PD) is a neurodegenerative disease with movement disorders including resting tremor, rigidity, bradykinesia and postural instability. Recent studies have identified a new PD associated gene, TMEM230 (transmembrane protein 230). However, the pathological roles of TMEM230 and its variants are not fully understood. TMEM230 gene encodes two protein isoforms. Isoform2 is the major protein form (~95%) in human. In this study, we overexpress isoform2 TMEM230 variants (WT or PD-linked *184Wext*5 mutant) or knockdown endogenous protein in cultured SH-5Y5Y cells and mouse primary hippocampus neurons to study their pathological roles. We found that overexpression of WT and mutant TMEM230 or knockdown of endogenous TMEM230-induced neurodegeneration and impaired mitochondria transport at the retrograde direction in axons. Mutant TMEM230 caused more severe neurotoxicity and mitochondrial transport impairment than WT-TMEM230 did. Our results demonstrate that maintaining TMEM230 protein levels is critical for neuron survival and axon transport. These findings suggest that mutant-TMEM230-induced mitochondrial transport impairment could be the early event leading to neurite injury and neurodegeneration in PD development.

Transmembrane Protein 230 Mediates a Poly(ADP-ribose) Polymerase-1-Linked Apoptosis.

Mutations in transmembrane protein 230 (TMEM230) gene are suggested to be associated with the autosomal dominant Parkinson’s disease (PD) with typical movement disorders and Lewy body pathology. However, the normal functions and the pathological roles of TMEM230 are not clear. In this study, we used TMEM230 isoform II constructs including wild-type (WT) and four reported PD-linked mutation constructs (Y92C, R141L, 184Wext*5, and 184PGext*5). Ectopic expression of WT and 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. Moreover, 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. Our results indicated that TMEM230 mediated a PARP1-linked apoptotic cell death pathway. These findings not only provide the novel insight into the biological roles of TMEM230 in the PARP1-linked pathway but also provide a TMEM230-induced cell death mechanism underlying PD pathogenesis.

Lack of TMEM230 mutations in patients with familial and sporadic Parkinson's disease in a Taiwanese population.

Mutations in transmembrane protein 230 (TMEM230) have recently been reported to be associated with Parkinson's disease (PD) in a North American population. A highly prevalent mutation, c.550_552delTAGinsCCCGGG (p.*184ProGlyext*5) was found in 3.1% of Chinese familial PD patients. However, subsequent studies failed to replicate these findings in different populations. Our objective was to confirm the role of this gene in a large number of PD patients and controls in a Taiwanese population. Among 1,672 participants, we sequenced all coding exons and exon-intron boundary junctions of the TMEM230 gene in 180 probands with familial PD. We also genotyped the potential pathogenic variants identified and the previously reported mutations (p.Arg141Leu, p.Tyr92Cys, p.*184Trpext*5, and p.*184ProGlyext*5) in an additional cohort of 500 patients with sporadic PD, and 992 age and gender-matched neurologically normal control subjects. We did not find any of the previously reported mutations, but we observed one novel missense exonic variant, c.G68A (p.Arg23Gln), in one patient with familial PD, and two patients with sporadic PD in a heterozygous state. However, subsequent analysis of this variant in 992 controls did not find any significant associations between p.Arg23Gln and the risk of PD (0.44% vs. 0.30%, p = 0.22). Our findings suggest that genetic variants of TMEM230 do not play a major role in PD in our Taiwanese population. Further experimental studies are warranted to confirm the pathogenicity of this gene in PD disease process.

TMEM230 Accumulation in Granulovacuolar Degeneration Bodies and Dystrophic Neurites of Alzheimer's Disease.

Transmembrane Protein 230 (TMEM230) is a newly identified protein associated with Parkinson's disease (PD) found in Lewy bodies and Lewy neurites of patients with PD or dementia with Lewy body disease. However, TMEM230 has not yet been investigated in the most common neurodegenerative disorder, Alzheimer's disease (AD). Here, we demonstrate that the expression of TMEM230 is specifically increased in neurons in AD patients. Importantly, both granulovacuolar degeneration (GVD) and dystrophic neurites (DNs), two prominent characteristic pathological structures associated with AD, contain TMEM230 aggregates. TMEM230 immunoreactivity can be detected in neurofibrillary tangles-containing neurons and hyperphosphorylated tau positive DNs. TMEM230 accumulation is also noted around senile plaques. These findings identifying TMEM230 as a component of GVD and DNs suggest TMEM230 dysregulation as a likely mechanism playing an important role in the pathogenesis of AD.

TMEM230: How does it fit in the etiology and pathogenesis of Parkinson's disease?

Mutations in the transmembrane protein 230 (TMEM230) gene were recently identified in a large Canadian pedigree and 7 smaller Chinese families, nominating TMEM230 as the third gene causing a Mendelian form of late onset Parkinson's disease (PD) with typical Lewy-body pathology (after synuclein alpha (SNCA) and leucine rich repeat kinase 2 (LRRK2)). The protein encoded by TMEM230 remains largely uncharacterized, but initial evidence points to roles in the trafficking of recycling vesicles, retromers, and endosomes, suggesting intriguing links to the pathways targeted by other PD-causing genes. The focus on family-based studies is gaining new momentum in the next-generation sequencing era, for the discovery of further, high-penetrance (medically relevant) genetic variants in PD. However, at this junction, important aspects of the TMEM230 story remain unclear, such as the prevalence of these mutations in the Chinese and other populations of the world, the penetrance of the mutations, and even their mode of inheritance. The first replication studies among Chinese and White PD patients have been largely negative. Furthermore, much more work remains ahead to elucidate the mechanisms by which these mutations might lead to neuronal cell death, alpha-synuclein pathology, and parkinsonism. © 2017 International Parkinson and Movement Disorder Society.

TMEM230 Mutations Are Rare in Han Chinese Patients with Autosomal Dominant Parkinson's Disease.

Mutations in the gene encoding the transmembrane protein 230 (TMEM230) have been reported in patients with familial, autosomal dominant inherited Parkinson's disease (ADPD). The aim of the present study was to explore the role and the prevalence of TMEM230 mutations in Chinese patients with ADPD. A cohort of 120 patients with ADPD and 650 healthy controls (HCs) from the Department of Neurology, West China Hospital of Sichuan University was screened. The entire coding exons of TREM230 in all the patients, as well as exon 5 of this gene in the 650 HCs, were directly sequenced with the Sanger sequencing approach. Novel identified mutations or variants of Parkinson's disease were tested in all HCs in the corresponding chromosomal regions. Two novel variants of the TMEM230 gene were identified. The c.46G>T [p. Gly16Trp] variant in exon 1 was identified in a male PD patient, while a heterozygous frameshift variant, c.429delT [p. Val143ValfsX4], in exon 5 was found in an HC. However, the most commonly reported mutation, p.*184ProGlyext*5, was not detected in either the patients or control subjects in this study. Our findings suggested that TMEM230 mutations are very rare in the ADPD Han Chinese population. Further evaluation of genetic data from a larger sample population is required to understand the genetic role of TMEM230 in the etiology of PD.