MG-115

MG-115 is a potent inhibitor with Kis of 21 nM and 35 nM for 20S and 26S proteasome, respectively ^[1].

MG-115 (50 μM, 2 h) increased the expression of the insulin receptor and its mature beta subunit by a factor of 3 and 4.2, respectively in Leu1193 and Asp1179 COS-7 mutant cell lines^[2].Treated Rat-1 and PC12 cells with MG-115(30 μM, 4 h) can induced apoptosis of both cell types^[3]. Iisolated rat islets were cultured and pre-treated with proteasome inhibitors and subsequently exposed for 48 h to 25 U/ml human IL-1beta. Pre-treatment with 10 uM of the proteasome inhibitor MG-115 counteracted the suppressive effects^[4]. HCC cells SK-Hep1, HLE and HepG2 were treated with the proteasome inhibitors MG-115. MG-115 induce apoptosis in the three cell types tested in a dose-dependent manner. MG-115 downregulated expression of XIAP in SK-Hep1, and survivin in SK-Hep1 and HepG2^[5]. MG-115 decreased within 120 min the aldosterone and corticosterone secretion from freshly dispersed zona glomerulosa and zona fasciculata-reticularis (ZF/R) cells. After a 24-h incubation MG-115 alone lowered corticosterone production and enhanced proliferation rate of cultured ZF/R cells^[6]. The proteasome inhibitor MG-115 can inhibit ATF6, which is the direct target of the proteasome-ubiquitin pathway^[7]. MG-115 was diminished by adding at a time corresponding to the half time required for germinal vesicle breakdown. Potent inhibition of germinal vesicle breakdown was also observed by microinjection of anti-proteasome-a-subunit antibodies^[8]. MG-115 induced a decrease in Bid, Bcl-2, and survivin protein levels, an increase in Bax, loss of the mitochondrial transmembrane potential, cytochrome c release, activation of caspases (-8, -9 and -3), and an increase in the tumor suppressor p53 levels in PC3^[9].

References:
[1]. Rock KL, Gramm C, et,al. Inhibitors of the proteasome block the degradation of most cell proteins and the generation of peptides presented on MHC class I molecules. Cell. 1994 Sep 9;78(5):761-71. doi: 10.1016/s0092-8674(94)90462-6. PMID: 8087844.
[2]. Imamura T, Haruta T, et,al. Involvement of heat shock protein 90 in the degradation of mutant insulin receptors by the proteasome. J Biol Chem. 1998 May 1;273(18):11183-8. doi: 10.1074/jbc.273.18.11183. PMID: 9556607
[3]. Lopes UG, Erhardt P, et,al. p53-dependent induction of apoptosis by proteasome inhibitors. J Biol Chem. 1997 May 16;272(20):12893-6. doi: 10.1074/jbc.272.20.12893. PMID: 9148891.
[4]. Sternesj? J, Karlsen AE, et,al.Involvement of the proteasome in IL-1beta induced suppression of islets of Langerhans in the rat. Ups J Med Sci. 2003;108(1):37-50. doi: 10.3109/2000-1967-122. PMID: 12903836.
[5]. Inoue T, Shiraki K, et,al. Proteasome inhibition sensitizes hepatocellular carcinoma cells to TRAIL by suppressing caspase inhibitors and AKT pathway. Anticancer Drugs. 2006 Mar;17(3):261-8. doi: 10.1097/00001813-200603000-00004. PMID: 16520654.
[6]. Ziolkowska A, Tortorella C, et,al.Accumulation of steroidogenic acute regulatory protein mRNA, and decrease in the secretory and proliferative activity of rat adrenocortical cells in the presence of proteasome inhibitors. Int J Mol Med. 2006 May;17(5):865-8. PMID: 16596272.
[7]. Hong M, Li M, et,al. Endoplasmic reticulum stress triggers an acute proteasome-dependent degradation of ATF6. J Cell Biochem. 2004 Jul 1;92(4):723-32. doi: 10.1002/jcb.20118. PMID: 15211570.
[8].Takagi Sawada M,et,al. The proteasome is an essential mediator of the activation of pre-MPF during starfish oocyte maturation. Biochem Biophys Res Commun. 1997 Jul 9;236(1):40-3. doi: 10.1006/bbrc.1997.6900. PMID: 9223422.
[9].Nam YJ, Lee DH, et,al. 3,4,5-tricaffeoylquinic acid attenuates proteasome inhibition-mediated programmed cell death in differentiated PC12 cells. Neurochem Res. 2014 Aug;39(8):1416-25. doi: 10.1007/s11064-014-1327-x. Epub 2014 May 14. PMID: 24825618.