探討 CBAP 在 Akt/TSCC/Rheb/mTORC1 胰島素的刺激及活化中的角色

Study on the role of CBAP in insulin stimulated activation of the Akt/TSCC/Rheb/mTORC1 signaling pathway

廖偉廷(Wei-Ting Liao)

指導教授 ： 嚴仲陽

國立臺灣大學/醫學院/分子醫學研究所/博士(2022年)

https://doi.org/10.6342/NTU202202252

摘要

在正常或癌化的細胞中，Akt-Rheb-mTORC1 訊息途徑調控許多重要的生理代謝作用。然而，Akt如何透過影響Tuberous Sclerosis Complex protein complex (TSCC)的GTPase-activating protein (GAP)活性，進而調控Rheb的活性的機制，並不全然清楚。在本研究中我們提供證據描述一個訊息傳遞複合體，稱作TSC2-Akt-CBAP complexes controlling Rheb Desuppression (TACRD)，可以藉由在溶酶體的表面上的CBAP調控TSC1/TSC2的結合，進而影響到TSCC的GAPase活性，以此來控制生長激素刺激之下Rheb的活性。我們的細胞內以及試管內實驗一致顯示，CBAP可以藉由其N端的疏水區域，與TSC1競爭TSC2 的HBD片段的結合，來調節TACRD的GAPase功能。更進一步，在溶酶體的表面上高量表達的CBAP，會透過一種TSC2依賴的機制，不儘可以活化mTORC1訊息途徑, 也能導致溶酶體生成變多，與TSC2基因缺失對於細胞生理影響的表現型相似。因此我們的研究揭露了另外一種抑制TSC2活性的機制，以及更進一步顯示CBAP在mTORC1調控溶酶體生成以及細胞生長的訊號途徑中扮演一定的角色。

關鍵字

Akt ； Rheb small GTPase ； TSC2 deficiency ； CBAP ； 細胞生長調控 ； TFEB ； mTORC1 activation

並列摘要

The Akt-Rheb-mTORC1 signaling axis controls many crucial pathways in normal and tumorous cells. However, how Akt regulates the GTPase-activating protein (GAP) activity of Tuberous Sclerosis Complex protein complex (TSCC) on the small GTPase Rheb is incompletely understood. We provide evidence for a signaling platform, termed TSC2-Akt-CBAP complexes controlling Rheb Desuppression (TACRD), operating on lysosomal membranes where CBAP and growth factor stimulation regulate TSC1/TSC2 association and the GAP activity of TSCC towards Rheb. Our in vitro and in vivo assays reveal that CBAP modulates TACRD function partly by competing with TSC1 for binding with the harmatin-binding domain of TSC2 via the CBAP N-terminal hydrophobic domain. Lysosomal enrichment of CBAP not only activated mTORC1 signaling pathway, but also enhanced lysosomal biogenesis via a TSC2-dependent mechanism, phenocopying TSC2-null phenotypes. Our study reveals an alternative TSC2-inactivation mechanism and underscores the importance of CBAP to mTORC1-mediated regulation and lysosomal biogenesis during cell growth and oncogenesis.

並列關鍵字

Akt ； Rheb small GTPase ； TSC2 deficiency ； CBAP ； cell growth control ； oncogenesis ； TFEB nuclear localization ； mTORC1 activation

參考文獻

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