Fascaplysin has been reported to exert anti-cancer effects by inhibiting cyclin-dependent kinase 4 (CDK4); however, the precise mode of action by which fascaplysin suppresses tumor growth is not clear. Here, we found that fascaplysin has stronger anti-cancer effects than other CDK4 inhibitors, including PD0332991 and LY2835219, on lung cancer cells that are wild-type or null for retinoblastoma (RB), indicating that unknown target molecules might be involved in the inhibition of tumor growth by fascaplysin. Fascaplysin treatment significantly decreased tumor angiogenesis and increased cleaved-caspase-3 in xenografted tumor tissues. In addition, survivin and HIF-1α were downregulated in vitro and in vivo by suppressing 4EBP1-p70S6K1 axis-mediated de novo protein synthesis. Kinase screening assays and drug-protein docking simulation studies demonstrated that fascaplysin strongly inhibited vascular endothelial growth factor receptor 2 (VEGFR2) and tropomyosin-related kinase A (TRKA) via DFG-out non-competitive inhibition. Overall, these results suggest that fascaplysin inhibits TRKA and VEGFR2 and downregulates survivin and HIF-1α, resulting in suppression of tumor growth. Fascaplysin, therefore, represents a potential therapeutic approach for the treatment of multiple types of solid cancer.

Myotubularin-related protein 1 (MTMR1) is a phosphatase that belongs to the tyrosine/dual-specificity phosphatase superfamily. MTMR1 has been shown to use phosphatidylinositol 3-monophosphate (PI(3)P) and/or phosphatidylinositol 3,5-bisphosphate (PI(3,5)P₂) as substrates. Here, we determined the crystal structure of human MTMR1. The refined model consists of the Pleckstrin homology (PH)-GRAM and phosphatase (PTP) domains. The overall structure was highly similar to the previously reported MTMR2 structure. Interestingly, two phosphate molecules were coordinated by strictly conserved residues located in the C(X)₅R motif of the active site. Additionally, our biochemical studies confirmed the substrate specificity of MTMR1 for PI(3)P and PI(3,5)P₂ over other phosphatidylinositol phosphates. Our structural and enzymatic analyses provide insight into the catalytic mechanism and biochemical properties of MTMR1.

RNA polymerase II carboxyl-terminal domain (pol II CTD) phosphatases are a newly emerging family of phosphatases that are members of DXDX (T/V). The subfamily includes Small CTD phosphatases, like SCP1, SCP2, SCP3, TIMM50, HSPC129 and UBLCP. Extensive study of SCP1 has elicited the diversified roles of the small C terminal domain phosphatase. The SCP1 plays a vital role in various biological activities, like neuronal gene silencing and preferential Ser5 dephosphorylation, acts as a cardiac hypertrophy inducer with the help of its intronic miRNAs, and has shown a key role in cell cycle regulation. This short review offers an explanation of the mechanism of action of small CTD phosphatases, in different biological activities and metabolic processes.

The human C-terminal domain small phosphatase 1 (CTDSP1/SCP1) is a protein phosphatase with a conserved catalytic site of DXDXT/V. CTDSP1’s major activity has been identified as dephosphorylation of the 5th Ser residue of the tandem heptad repeat of the RNA polymerase II C-terminal domain (RNAP II CTD). It is also implicated in various pivotal biological activities, such as acting as a driving factor in repressor element 1 (RE-1)-silencing transcription factor (REST) complex, which silences the neuronal genes in non-neuronal cells, G1/S phase transition, and osteoblast differentiation. Recent findings have denoted that negative regulation of CTDSP1 results in suppression of cancer invasion in neuroglioma cells. Several researchers have focused on the development of regulating materials of CTDSP1, due to the significant roles it has in various biological activities. In this review, we focused on this emerging target and explored the biological significance, challenges, and opportunities in targeting CTDSP1 from a drug designing perspective.

Background: Diabetes mellitus (DM) is a chronic progressive metabolic disease that involves uncontrolled elevation of blood glucose levels. Among various therapeutic approaches, GLP-1 prevents type 2 diabetes mellitus (T2DM) patients from experiencing hyperglycemic episodes. However, the short half-life (< 5 min) and rapid clearance of GLP-1 often limits its therapeutic use. Here, we developed an oral GLP-1 gene delivery system to achieve an extended antidiabetic effect. Methods: Human IgG1 (hIgG1)-Fc-Arg/pDNA complexes were prepared by an electrostatic complexation of the expression plasmid with various ratios of the positively modified Fc fragments of an antibody (hIgG1-Fc-Arg) having a targeting ability to FcRn receptor. The shape and size of the complexes were examined by atomic force and field emission electron microscope. The stability of the complexes was tested in simulated gastrointestinal pH and physiological serum condition. Cellular uptake, transport, and toxicity of the complexes were tested in the Caco-2 cells. Biodistribution and antidiabetic effect of the complexes were observed in either Balb/c mice or Lep _db/db mice. Results: A 50/1 ratio of the hIgG1-Fc-Arg/pDNA produced a complex structure having approximately 40 ~ 60 nm size and also demonstrated protection of pDNA in the complex from the physiological pH and serum conditions. Cellular uptake and transport of the complex were demonstrated in Caco-2 cells having FcRn receptor expression and forming the monolayer-polarized structure. The cellular toxicity of both delivery vehicle and the complex revealed their minimal toxicity comparable with nontoxicity of a commercial transfection reagent. Biodistribution of the complex showed the detectable distribution of the complex in the most parts of gastrointestinal tract due to ubiquitous expression of the FcRn receptors. An in vivo type 2 diabetes treatment study of oral administration of hIgG1-Fc-9Arg/pGLP-1 complexes showed absorption and expression in GI tract of either Balb/c mice or Lep _db/db mice. Conclusion: In this study, we developed an oral GLP-1 gene delivery system on the platform of cationic hIgG1-Fc-9Arg. Prolonged t1/2, less immunoactivity, and better bioactivities of hIgG-Fc-9Arg/pGLP-1 complexes appeared to be a promising approach to achieve potent treatment of type 2 diabetes treatment.