dRAGging Amino Acid-mTORC1 Signaling by SH3BP4

Pancreatic cancer is one of the most lethal and aggressive cancers in the world. However, no effective treatment is currently available for pancreatic cancer. The objective of this study was to determine the anti-pancreatic cancer effect of α-mangostin (αM) and γ-mangostin (γM) extracted from the pericarp of Garcinia mangostana L.. Both αM and γM reduced the viability of pancreatic cancer cells MIA PaCa-2 and PANC-1 in a dose-dependent manner. These compounds induced apoptosis by increasing c-PARP and c-Caspase 3 levels. They also induced autophagy by increasing levels of microtubule-associated protein 1A/1B light chain 3B (LC3II) in both cell lines while decreasing sequestosome 1 (p62) in MIA PaCa-2. Both αM and γM induced autophagy through increasing phosphorylation levels of AMP-activated protein kinase (p-AMPK) and p38-mitogen activated protein kinase (p-p38) while decreasing phosphorylation level of mammalian target of rapamycin complex 1 (p-mTOR). Of various microRNAs (miRNA), miR-18a was found to be a putative regulatory miRNA for autophagy induced by αM or γM. In combination with gemcitabine, a compound frequently used in pancreatic cancer treatment, αM and γM showed synergistic anti-cancer effects in MIA PaCa-2. Collectively, these results suggest that αM and γM can induce apoptosis and autophagy in pancreatic cancer cells and that their anti-cancer effect is likely to be associated with miR-18a. In conclusion, αM and γM might be used as a potential new therapy for pancreatic cancer.

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“…SH3BP4 is a negative regulator of RagGTPases. It inhibits mTORC1 ( Kim and Kim, 2013 ). It may have potential to induce autophagy.…”

Section: Discussionmentioning

confidence: 99%

α, γ-Mangostins Induce Autophagy and Show Synergistic Effect with Gemcitabine in Pancreatic Cancer Cell Lines

Kim

Chin

2017

Biomolecules & Therapeutics

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“…Previous studies have shown that the SH3BP4 protein is localized to the plasma membrane, perinuclear region, and clathrin-coated vesicles (Kim and Kim, 2013, Kim et al., 2012, Tosoni et al., 2005). In concordance with the previous studies, we confirmed that WT SH3BP4 was predominantly expressed at the perinuclear region (Figure 4H).…”

Section: Resultsmentioning

confidence: 99%

SH3BP4 Regulates Intestinal Stem Cells and Tumorigenesis by Modulating β-Catenin Nuclear Localization

et al. 2019

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Summary Wnt signals at the base of mammalian crypts play a pivotal role in intestinal stem cell (ISC) homeostasis, whereas aberrant Wnt activation causes colon cancer. Precise control of Wnt signal strength is governed by a number of negative inhibitory mechanisms acting at distinct levels of the cascade. Here, we identify the Wnt negative regulatory role of Sh3bp4 in the intestinal crypt. We show that the loss of Sh3bp4 increases ISC and Paneth cell numbers in murine intestine and accelerates adenoma development in Apc min mice. Mechanistically, human SH3BP4 inhibits Wnt signaling downstream of β-catenin phosphorylation and ubiquitination. This Wnt inhibitory role is dependent on the ZU5 domain of SH3BP4. We further demonstrate that SH3BP4 is expressed at the perinuclear region to restrict nuclear localization of β-catenin. Our data uncover the tumor-suppressive role of SH3BP4 that functions as a negative feedback regulator of Wnt signaling through modulating β-catenin’s subcellular localization.

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“…Many virally encoded inhibitors of autophagy have been discovered (21)(22)(23), and such a function has also been reported for MC159 (20). Since SH3BP4 has also been independently linked to the autophagic regulation (42,43), it was of particular interest to examine the capacity of MC159 and its SH3BP4 binding-deficient mutant to regulate cellular autophagy. To this end, we used a lentiviral vector to stably transduce wild-type MC159 and MC159 AXXA(N) fused with the red fluorescent protein mCherry into a previously characterized MCF7-derived macroautophagy reporter cell line expressing the LC3 protein fused to enhanced green fluorescent (MCF-7/LC3-EGFP cells) (44).…”

Section: Figmentioning

confidence: 97%

MC159 of Molluscum Contagiosum Virus Suppresses Autophagy by Recruiting Cellular SH3BP4 via an SH3 Domain-Mediated Interaction

Schmotz

Uğurlu

Vilén

et al. 2019

J Virol

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MC159 is a viral FLIP (FLICE inhibitory protein) encoded by the molluscum contagiosum virus (MCV) enabling MCV to evade antiviral immunity and to establish persistent infections in humans. Here, we show that MC159 contains a functional SH3 binding motif, which mediates avid and selective binding to SH3BP4, a signaling protein known to regulate endocytic trafficking and suppress cellular autophagy. The capacity to bind SH3BP4 was dispensable for regulation of NF-Bmediated transcription and suppression of proapoptotic caspase activation but contributed to inhibition of amino acid starvation-induced autophagy by MC159. These results provide new insights into the cellular functions of MC159 and reveal SH3BP4 as a novel host cell factor targeted by a viral immune evasion protein.IMPORTANCE After the eradication of smallpox, molluscum contagiosum virus (MCV) is the only poxvirus restricted to infecting humans. MCV infection is common and causes benign skin lesions that usually resolve spontaneously but may persist for years and grow large, especially in immunocompromised individuals. While not life threatening, MCV infections pose a significant global health burden. No vaccine or specific anti-MCV therapy is available. MCV encodes several proteins that enable it to evade antiviral immunity, a notable example of which is the MC159 protein. In this study, we describe a novel mechanism of action for MC159 involving hijacking of a host cell protein called SH3BP4 to suppress autophagy, a cellular recycling mechanism important for antiviral immunity. This study contributes to our understanding of the host cell interactions of MCV and the molecular function of MC159. KEYWORDS MC159, MVC, SH3 domain, SH3BP4, autophagy, protein-protein interactions, vFLIP Citation Schmotz C, Ug urlu H, Vilen S, Shrestha S, Fagerlund R, Saksela K. 2019. MC159 of molluscum contagiosum virus suppresses autophagy by recruiting cellular SH3BP4 via an SH3 domain-mediated interaction. J Virol on July 11, 2020 by guest http://jvi.asm.org/ Downloaded from FIG 3 Association of MC159 with SH3BP4 in human cells. Biotin acceptor domain-tagged MC159 or the indicated PXXP motif mutants were transfected into 293T cells together with Myc-tagged SH3BP4 (A) or SH3BP4 alone (B). Lysates of these cells were examined by Western blotting either directly (cell lysates) or after precipitation with streptavidin-coated beads (MC159 pulldown) by probing the membranes using labeled streptavidin (MC159) or anti-Myc (A) or anti-SH3BP4 (B) antibodies. Schmotz et al. on July 11, 2020 by guest http://jvi.asm.org/ Downloaded from FIG 6 Regulation of autophagy by MC159 and its SH3BP4 binding-deficient mutant. (A and B) Control MCF-7/LC3-EGFP cells or their lentivirally transduced derivatives stably expressing wild-type MC159 or MC159 AXXA(N) were examined under normal culture conditions (A) or after 6 h of starvation (B) in medium lacking amino acids and serum using fluorescence microscopy imaging of nuclear (Hoechst)-, LC3-, and MC159-specific signals, as indicated. (C) Uniform ...

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dRAGging Amino Acid-mTORC1 Signaling by SH3BP4

Cited by 14 publications

References 53 publications

α, γ-Mangostins Induce Autophagy and Show Synergistic Effect with Gemcitabine in Pancreatic Cancer Cell Lines

α, γ-Mangostins Induce Autophagy and Show Synergistic Effect with Gemcitabine in Pancreatic Cancer Cell Lines

SH3BP4 Regulates Intestinal Stem Cells and Tumorigenesis by Modulating β-Catenin Nuclear Localization

MC159 of Molluscum Contagiosum Virus Suppresses Autophagy by Recruiting Cellular SH3BP4 via an SH3 Domain-Mediated Interaction

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