para-amino-Blebbistatin is a more water-soluble form of (S)-4'-nitro-blebbistatin , which is a more stable and less phototoxic form of (-)-blebbistatin .1,2,3 (-)-Blebbistatin is a selective cell-permeable inhibitor of non-muscle myosin II ATPases that rapidly and reversibly inhibits Mg-ATPase activity and in vitro motility of non-muscle myosin IIA and IIB for several species (IC50s = 0.5-5 μM), while poorly inhibiting smooth muscle myosin (IC50 = 80 μM).2,3,4 Through these effects, it blocks apoptosis-related bleb formation, directed cell migration, and cytokinesis in vertebrate cells. However, prolonged exposure to blue light (450-490 nm) results in degradation of blebbistatin to an inactive product via cytotoxic intermediates, which may be problematic for its use in fluorescent live cell imaging applications.5,6 The addition of a 4'-amino group increases its water solubility, decreases the inherent fluorescence, stabilizes the molecule to circumvent its degradation by prolonged blue light exposure, and decreases its phototoxicity while retaining the in vitro and in vivo activity of blebbistatin.7 para-amino-Blebbistatin has the same stereochemistry as the active (-)-blebbistatin enantiomer.
|1. Várkuti, B.H., Képiró, M., Horváth, I.á., et al. A highly soluble, non-phototoxic, non-fluorescent blebbistatin derivative. Sci. Rep. 6:26141, (2016).|2. Straight, A.F., Cheung, A., Limouze, J., et al. Dissecting temporal and spatial control of cytokinesis with a myosin II inhibitor. Science 299(5613), 1743-1747 (2003).|3. Kovács, M., Tóth, J., Hetényi, C., et al. Mechanism of blebbistatin inhibition of myosin II. J. Biol. Chem. 279(34), 35557-35563 (2004).|4. Limouze, J., Straight, A.F., Mitchison, T., et al. Specificity of blebbistatin, an inhibitor of myosin II. J. Muscle Res. Cell Motil. 25(4-5), 337-341 (2004).|5. Kolega, J. Phototoxicity and photoinactivation of blebbistatin in UV and visible light. Biochem. Biophys. Res. Commun. 320(3), 1020-1025 (2004).|6. Sakamoto, T., Limouze, J., Combs, C.A., et al. Blebbistatin, a myosin II inhibitor, is photoinactivated by blue light. Biochemistry 44(2), 584-588 (2005).|7. Verhasselt, S., Roman, B.I., Bracke, M.E., et al. Improved synthesis and comparative analysis of the tool properties of new and existing D-ring modified (S)-blebbistatin analogs. Eur. J. Med. Chem. 136, 85-103 (2017). |
TPC2-A1-P is a powerful and membrane permeable agonist of two pore channel 2 (TPC2) with an EC50 of 10.5 μM. TPC2-A1-P plays its role by mimicking the physiological actions of PI(3,5)P2. TPC2-A1-P also shows higher potency to induce Na2+ mobilisation from TPC2 than TPC-A1-N . TPC2-A1-P can be used to probe different functions of TPC2 channels in intact cells[1][2][3].
Two-pore channels (TPC1-3) are ancient members of the voltage-gated ion channel superfamily. TPCs are expressed throughout the endo-lysosomal system and regulates the trafficking of various cargoes[1].TPC2 can mediate different physiological and possibly pathophysiological effects depending on how it is activated. The ion selectivity of TPC2 is not fixed but rather agonist-dependent. TPC2 is a unique example of an ion channel that conducts different ions in response to different activating ligands[1].TPC2-A1-P (10 μM) reproducibly evokes Ca2+ signals, and TPC2-A1-P response reachs its plateau slower than TPC2-A1-N . The EC50 in full concentration-effect relationships for the plateau response is 10.5 μM for TPC2-A1-P in a cell line stably expressing TPC2L11A/L12A.TPC2-A1-P (10-30 μM) induces Ca2+ signals in Hela cells expressing TPC2 in the presence but not absence of extracellular Ca2+. However, the responses are smaller and delayed compared to TPC2-A1-N , consistent with the results obtained in cells stably expressing TPC2L11A/L12A. TPC2-A1-P fails to induce Ca2+ signals in cells expressing ’pore-dead’ TPC2L11A/L12A/L265P and also fails to evoke Ca2+ signals in cells expressing human TRPML1 re-routed to the plasma membrane (TRPML1δNC)[1].In endo-lysosomal patch-clamp experiments, TPC2-A1-P (10 μM) evokes currents in endo-lysosomes isolated from cells expressing TPC2 and TPC2M484L, the currents evoked by TPC2-A1-P are significantly larger than those evoked by TPC2-A1-N in both wild-type and gain-of-function variant,and exhibits an EC50 value of 0.6 μM for TPC2-A1-P[1].
[1]. Susanne Gerndt, et al. Agonist-mediated switching of ion selectivity in TPC2 differentially promotes lysosomal function. Elife. 2020 Mar 16;9:e54712. [2]. Gerndt S, et al. Discovery of lipophilic two-pore channel agonists. FEBS J. 2020;287(24):5284-5293. [3]. Xuhui Jin, et al. Targeting Two-Pore Channels: Current Progress and Future Challenges. Trends Pharmacol Sci. 2020 Aug;41(8):582-594. |