인문학
사회과학
자연과학
공학
의약학
농수해양학
예술체육학
복합학
DBpia AI
AI 에이전트
AI 아이디어
AI 리더
AI 뷰어
Citeasy
크롬 서지관리 다운로드
지원사업
학술연구/단체지원/교육 등 연구자 활동을 지속하도록 DBpia가 지원하고 있어요.
커뮤니티
연구자들이 자신의 연구와 전문성을 널리 알리고, 새로운 협력의 기회를 만들 수 있는 네트워킹 공간이에요.
초록·키워드
In normal human bone remodeling, osteoclastic bone resorption is a highly coordinated and multi-pronged process, under the indirect hormonal control of parathyroid hormone. Once stimulated, several mechanisms must work in-concert to drive the digestion of bone. This includes proper attachment of integrin on the osteoclast to osteopontin on the bone surface, acidification of Howship's Lacunae, and transport of enzymes and dissolved bone matrix. Rab GTPases are a class of G-proteins that have been implicated in vesicular transport within the osteoclast. Rab7 specifically plays a pivotal role in the secretory lysosomal pathway, which delivers HCl and Cathepsin K to the resorption lacunae for bone digestion. Additionally, it is also involved in the transcytotic route, wherein type I collagen, TGFB, and osteocalcin migrate from the ruffled border to the functional secretory domain. The regulation of Rab7 is tightly controlled, with GTPase accelerating-proteins (GAPs) inhibiting Rab7 through promotion of its intrinsic GTPase activity. Armus is a GAP whose interaction with Rab7 is well elucidated. The catalytic process involves two key residues of Armus, R55 and Q92, which access a basic cleft of Rab7 which houses GTP. R55 attracts and positions the terminal phosphate group whereas Q92 recruits a water molecule to execute the hydrolysis reaction. While this mechanism is well established, the upstream regulation of Armus is understudied, especially by the other G-proteins, Rab5 and Rac1 that have been postulated to function as inhibitors of Armus. In this study, we have conducted a comprehensive computational analysis of Rab7, Rab5, and Rac1 interactions with Armus. Using sequence analysis, protein-protein docking, and in silico mutagenesis experiments, we elucidate the structure-function relationships of the various interacting partners of Armus. Our results show that Rab7 K38 adequately positions the arginine-finger of Armus for optimal dephosphorylation activity. In contrast, Rab5 and Rac1 have this residue substituted by E33 and P33 respectively, which instead attract R55 and misorient the residue, effectively hindering the hydrolysis mechanism. This is further validated by in silico mutagenesis experiments which predict that the substitutions, E33K and P33K promote an alternative scenario with a reconfigured interaction interface of the active site in the catalytic domain. Reciprocally, both the K38E and K38P mutations in Rab7 cause an unfavorable positioning of the R55 residue in its interaction with Armus. P33 in Rac1 and E33 in Rab5 also have the secondary function of increasing overall attraction to Armus that may aid in the displacement of Rab7. Rac1, Rab5, and the Rab7 mutants all exhibit increased polar contacts between R55 of Armus and the G-protein. Meanwhile, the Rac1/Rab5 mutants exhibit reduced recruitment of R55 in Armus, likely secondary to repulsion by the newly introduced K33 residues. Based on our results, we suggest that both Rab5 and Rac1 support the Rab7-mediated secretory lysosomal/transcytotic pathways by preferentially binding to Armus and dislodging Rab7. Furthermore, Rac1 and Rab5 also hinder Armus access to the GTP moiety, so that these proteins remain active in their various roles within the osteoclast. This investigation advances the current knowledge on bone physiology, providing useful information for the development of potential therapies against osteoporosis, osteoid tumors, osteitis fibrosa cystica, and other bone pathologies.
인공지능 문자 인식 모델을 통해 추출된 텍스트로, 일부 오타나 오류가 포함될 수 있으나 지속적으로 개선 중입니다.
오류를 발견하셨다면 해당 부분을 드래그한 후 ' 를 통해 신고해주세요.
오류를 발견하셨다면 해당 부분을 드래그한 후 ' 를 통해 신고해주세요.
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