Inositol polyphosphate multikinase (IPMK) and inositol hexakisphosphate 1 (IP6K1) are pleiotropic enzymes essential for the biosynthesis of inositol polyphosphate. However, little is known about the precise control of IPMK expression in macrophages. I observed that both mRNA and protein levels of IPMK were downregulated in TLR4-activated macrophages stimulated with lipopolysaccharide (LPS). miR-181c which is induced by LPS treatment was predicted to bind to the 3'UTR of mouse IPMK mRNA. I performed genomic deletion of miR-181c-binding sequence within IPMK 3'UTR. Stable IPMK expression in macrophages showed both TLR4-signaling events and proinflammatory cytokine induction were markedly attenuated at 2-6 hours of LPS treatment in mutant IPMK macrophages. IPMK was further shown to directly inhibit K63-linked ubiquitination of TRAF6 via direct interaction. Therefore, these findings reveal that this miRNA-181c-mediated suppression of IPMK as a nodal point of regulation for the resolution of TLR4 signaling and inflammation. Also, regarding tumor formation and progression, the role of host IP6K1 in this pathology remains poorly understood. Here I investigated whether host IP6K1 knockout (KO) could control tumor growth using a syngeneic MC38 model which is a syngeneic mouse colon adenocarcinoma tumor model on C57BL/6 background. Using the global IP6K1 KO mice, I showed that the absence of the host IP6K1 gives rise to significantly shortened survival than normal mice due to more rapidly growing tumors. By flow cytometric analysis, tumors in IP6K1 KO mice contained high levels of CD11b+Gr1+IL10+ myeloid cells and lower infiltration of M1-polarized tumor-associated macrophage (TAM), dendritic cell, and CD8 killer T cell into murine colon carcinoma tumors. These data indicate that host IP6K1 acts as a tumor suppressor to regulate anti-tumor immune activities and control the recruitment and activation of cytotoxic T cells to the primary tumor through reprogramming tumor-immune control, and loss of this pathway increases tumor progression.
본 연구에서 나는 지질다당류 자극 톨유사수용체4 활성화 대식세포에서 이노시톨 폴리포스페이트 멀티키나아제의 유전자와 단백질 수준이 감소됨을 관찰했고, 이는 마이크로RNA-181c에 의한 것으로 예측되었다. 이노시톨 폴리포스페이트 멀티키나아제 3’ 비번역부위에서 마이크로RNA-181c 결합 서열을 삭제한 대식세포주에서 지질다당류 자극 톨유사수용체4-신호전달 및 전염증성 사이토카인이 감소함을 확인했다. 이노시톨 폴리포스페이트 멀티키나아제는 직접적인 상호작용으로 종양괴사인자수용체-관련인자6의 K63 연결 유비퀴틴화를 억제했다. 이러한 발견은 이노시톨 폴리포스페이트 멀티키나아제가 톨유사수용체4 신호 전달 및 염증 조절의 노드 포인트임을 보였다. 또한 나는 호스트 이노시톨 육인산키나아제1의 종양 성장 제어 확인을 위해 동계 MC38 모델을 사용하였고, 이노시톨 육인산키나아제1 녹아웃 생쥐에서 종양의 더 빠른 성장을 관찰했다. 유세포 분석에 따르면 이노시톨 육인산키나아제1 녹아웃 생쥐의 종양에 M1 종양 관련 대식세포, 수지상 세포 및 CD8 킬러 T 세포가 야생형 생쥐의 종양보다 적게 침투했다. 이 결과는 호스트 이노시톨 육인산키나아제1가 종양 억제인자로서 작용함을 보였다.
