PMC:4608092 / 47357-53187 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/4608092","sourcedb":"PMC","sourceid":"4608092","source_url":"https://www.ncbi.nlm.nih.gov/pmc/4608092","text":"Discussion\nRNF213 is highly associated with MMD9,29 and is a causative gene for MMD.8 Although low angiogenesis has been reported with RNF213,14 functional deviations caused by R4810K have not been investigated. Given that upregulation of R4810K may be important in development of MMD, the environmental stimuli that induce RNF213 remain unknown. Additionally, there are no animal models enabling to recapture the low-angiogenesis phenotype.\nIn the present study, we systemically investigated the effects of RNF213 R4810K on angiogenesis to address these issues discussed above. We found that upregulation could be produced by inflammatory signals of IFNs in HUVECs and ECs established from iPS cells from unaffected subjects and MMD patients. Upregulation of RNF213 by IFNs was consistently accompanied by lower angiogenesis, and silencing RNF213 partially ameliorated inhibition of angiogenesis by IFN-β. We also showed that upregulation of RNF213 was mediated by STATx in the promoter of the RNF213 gene. These data collectively indicate that upregulation of RNF213 WT is causally associated with lower angiogenic activity after IFN-β exposure. Therefore, RNF213 is likely to be a mediator downstream of the IFN-β-signaling pathway in ECs that are primed by IFN-β in vivo. However, upregulation of RNF213 WT was not sufficient to elicit antiangiogenic signals independently, whereas upregulation of RNF213 R4810K was sufficient. This in vitro finding was further confirmed by the Tg animal model in hypoxia. RNF213 R4757K (R4810K ortholog) inhibited angiogenesis in mice that overexpressed RNF213 in ECs. However, none of the mice with upregulation of the WT in ECs, upregulation of R4757K in SMCs, or null Rnf213 inhibited angiogenesis. Taken together, these data indicate that RNF213 R4810K can inhibit angiogenesis under conditions of exposure to IFNs or hypoxia, whereas RNF213 WT can only inhibit angiogenesis in the IFN-signaling pathway. It should be addressed that the current study clearly demonstrated the primary role of ECs in angiogenesis. This finding demonstrated a sharp contrast, with an anticipation that SMCs plays a critical role in the development of vascular remodeling. Collectively, we successfully demonstrated substantial roles of RNF213 R4810K in the low-angiogenesis phenotype in response to environmental stimuli. However, the issue of whether known functional impairment (ie, inhibition of cellular proliferation14 or mitotic abnormalities15) associated with RNF213 R4810K is involved in reduced angiogenesis after hypoxia in EC-specific RNF213 R4757K Tg mice needs to be examined in the future.\nThe current results suggest that carriers of RNF213 R4810K may be susceptible to cerebral hypoxia because of insufficient angiogenesis if inflammation and hypoxia simultaneously occur. These IFNs are induced by viral and bacterial infections and are upregulated in autoimmune patients, who are often complicated by encephalitis.30 Our study may imply that IFNs initially play a major role and are causally associated with insufficient angiogenesis in infectious or autoimmune diseases with MMD, as observed in accumulated clinical cases of MMD.31\nIn the present study, we found that a mutation in the AAA+ module toward stabilization of oligomers is responsible for a low-angiogenesis phenotype. We showed that the Walker B motif in the first AAA+ module of RNF213 had an inhibitory effect on angiogenesis. In contrast, deletion of the first AAA+ module did not have any discernible effects on angiogenesis. Intriguingly, both mutations resulted in loss of ATPase activity, but the WEQ mutation resulted in stabilization of oligomers, whereas deletion of AAA+ did not result in oligomerization. If this is the case, RNF213 R4810K, which decreased angiogenic activity and resulted in loss of ATPase activity in our study, may stabilize oligomers once they are formed and thus impair angiogenesis, suggesting a dominant negative mechanism. Furthermore, absence of a discernible effect of upregulation of deletion of the first AAA+ RNF213 on angiogenesis is in agreement with an observation in RNF213 null mice in which angiogenesis was not inhibited in the brain after exposure to hypoxia. Collectively, the current data provide a premature, but novel, insight into the mechanism of RNF213 R4810K mutation. AAA+ is a class of proteins, most of which transduce phosphorus covalent bond energy of ATP into mechanical energy through conformational changes. This process is mediated by the chemical reactions of ATP binding and hydrolysis. We consider that R4810K may be trapped in the RNF213 oligomer state, thereby inhibiting conformational changes, similar to RNF213 WEQ. Rigorous 3D structure analysis is required with a focus on conformational interaction between R4810K and AAA modules.\nIn conclusion, the present data suggest that RNF213 R4810K carriers have lower angiogenic capacities, indicating that these carriers might be more susceptible to insults of cerebral hypoxia. The present study shows that IFNs are environmental factors. Importantly, lower angiogenic activity is causally linked with AAA+ function of RNF213. Nevertheless, the pathological process bridging lowered angiogenesis and abnormal SMC proliferation (ie, moyamoya vessel formation or stenosis of arteries in the ring of Willis) remains unknown. This issue needs to be addressed in future studies. Studies determining the roles of RNF213 in remodeling and maintenance of the vascular system could provide comprehensive mechanisms of not only MMD, but also stenotic lesions in cerebral arteries.32 Finally, a specific inhibitor of ATP binding to the Walker A motif in the first AAA+ is a promising therapeutic candidate. Such a therapeutic tool could improve hypoxic tolerance of the central nervous system in R4810K carriers.","divisions":[{"label":"Title","span":{"begin":0,"end":10}}],"tracks":[{"project":"2_test","denotations":[{"id":"26126547-21048783-55294646","span":{"begin":47,"end":48},"obj":"21048783"},{"id":"26126547-19921495-55294647","span":{"begin":49,"end":51},"obj":"19921495"},{"id":"26126547-21799892-55294648","span":{"begin":84,"end":85},"obj":"21799892"},{"id":"26126547-23850618-55294649","span":{"begin":142,"end":144},"obj":"23850618"},{"id":"26126547-23850618-55294650","span":{"begin":2445,"end":2447},"obj":"23850618"},{"id":"26126547-23994138-55294651","span":{"begin":2472,"end":2474},"obj":"23994138"},{"id":"26126547-15771573-55294652","span":{"begin":2957,"end":2959},"obj":"15771573"},{"id":"26126547-22688062-55294653","span":{"begin":3173,"end":3175},"obj":"22688062"},{"id":"26126547-23010677-55294654","span":{"begin":5599,"end":5601},"obj":"23010677"}],"attributes":[{"subj":"26126547-21048783-55294646","pred":"source","obj":"2_test"},{"subj":"26126547-19921495-55294647","pred":"source","obj":"2_test"},{"subj":"26126547-21799892-55294648","pred":"source","obj":"2_test"},{"subj":"26126547-23850618-55294649","pred":"source","obj":"2_test"},{"subj":"26126547-23850618-55294650","pred":"source","obj":"2_test"},{"subj":"26126547-23994138-55294651","pred":"source","obj":"2_test"},{"subj":"26126547-15771573-55294652","pred":"source","obj":"2_test"},{"subj":"26126547-22688062-55294653","pred":"source","obj":"2_test"},{"subj":"26126547-23010677-55294654","pred":"source","obj":"2_test"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"2_test","color":"#d793ec","default":true}]}]}}