W-7 hydrochloride

N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride) (W-7) causes increases in intracellular free Ca2+ levels in bladder female transitional carcinoma (BFTC) cells.[Pubmed:11205271]

Anticancer Res. 2000 Nov-Dec;20(6B):4355-9.

The effect of N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride) (W-7), a widely used calmodulin inhibitor, on intracellular free Ca2+ levels ([Ca2+]i) in bladder female transitional cancer (BFTC) cells was examined using fura-2 as a Ca2+ dye. W-7 (10-1000 microM) caused an increase in [Ca2+]i in a concentration-dependent manner with an EC50 of 75 microM. The [Ca2+]i response was composed of an initial rise and a sustained plateau without significant decaying during the measurement of 250 seconds. Extracellular Ca2+ removal dramatically decreased the Ca2+ signals by 50-90%. W-7 (100 microM) failed to induce a [Ca2+]i increase in Ca(2+)-free medium after pretreatment with thapsigargin (1 microM), an endoplasmic reticulum Ca2+ pump inhibitor; conversely, W-7 pretreatment abolished the Ca2+ release induced by thapsigargin. Addition of 3 mM Ca2+ increased [Ca2+]i after preincubation with 100 microM W-7 in Ca(2+)-free medium. W-7-induced Ca2+ release was not altered by inhibiting phospholipase C with 2 microM 1-(6-((17b-3-methoxyestra-1,3,5 (10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione) (U73122). Together, this study shows that W-7 caused [Ca2+]i increases in human bladder cancer cells by releasing intracellular Ca2+ from the endoplasmic reticulum and also by causing extracellular Ca2+ influx with the later playing a dominant role. The W-7-induced intracellular Ca2+ release was uncoupled to a prior elevation in intracellular levels of inositol 1,4,5-trisphosphate (IP3).

The calmodulin antagonist W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride) inhibits DENV infection in Huh-7 cells.[Pubmed:27940224]

Virology. 2017 Jan 15;501:188-198.

Dengue virus (DENV) replicative cycle occurs in the endoplasmic reticulum where calcium ions play an important role in cell signaling. Calmodulin (CaM) is the primary sensor of intracellular Ca(2+) levels in eukaryotic cells. In this paper, the effect of the calmodulin antagonist W-7 in DENV infection in Huh-7 cells was evaluated. W7 inhibited viral yield, NS1 secretion and viral RNA and protein synthesis. Moreover, luciferase activity, encoded by a DENV replicon, was also reduced. A decrease in the replicative complexes formation was clearly observed in W7 treated cells. Docking simulations suggest 2 possible mechanisms of action for W7: the direct inhibition of NS2B-NS3 activity and/or inhibition of the interaction between NS2A with Ca(2+)-CaM complex. This last possibility was supported by the in vitro interaction observed between recombinant NS2A and CaM. These results indicate that Ca(2+)-CaM plays an important role in DENV replication.

Divergent pharmacological effects of three calmodulin antagonists, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), chlorpromazine and calmidazolium, on isometric tension development and myosin light chain phosphorylation in intact bovine tracheal smooth muscle.[Pubmed:2810127]

J Pharmacol Exp Ther. 1989 Nov;251(2):764-73.

To investigate the usefulness of calmodulin antagonists in intact cell systems, effects of three calmodulin antagonists, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), chlorpromazine (CPZ) and calmidazolium on isometric tension development and myosin light chain (P-LC) phosphorylation in bovine tracheal smooth muscle strips were compared to inhibition of purified myosin light chain kinase activity. These antagonists inhibited the Ca++-calmodulin-induced activation of myosin light chain kinase in a concentration-dependent manner, with IC50 values of 1.0 (calmidazolium), 25 (W-7) and 65 microM (CPZ), respectively. Inhibitory effects of these antagonists were abolished with increasing concentrations of calmodulin. However, when these antagonists were used in intact smooth muscle strips, the gradation of potencies did not parallel the anticalmodulin activities. W-7 (100 microM) exhibited a similar extent of antagonism between the contractile responses to carbachol and KCl. The increase in P-LC phosphate content in response to 1-min stimulation with 10(-5) M carbachol was inhibited by W-7. CPZ exhibited an unexpectedly potent antagonism on carbachol-induced isometric tension development and P-LC phosphorylation. Atropine showed an antagonism similar to CPZ. CPZ and verapamil had similar antagonistic effects on KCI-induced contractions. Calmidazolium (50 microM) produced no significant inhibition on carbachol-induced isometric tension development and P-LC phosphorylation in intact smooth muscle strips. It may be concluded that 1) W-7 antagonizes the smooth muscle contraction through the inhibition of the initial increase in the P-LC phosphorylation; 2) CPZ produces effects other than calmodulin antagonism; and 3) calmidazolium is not effective in intact smooth muscle strips.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct interaction of calmodulin antagonists with Ca2+/calmodulin-dependent cyclic nucleotide phosphodiesterase.[Pubmed:6099352]

J Biochem. 1984 Dec;96(6):1721-6.

Trypsin-treated Ca2+/calmodulin-dependent phosphodiesterase (CA2+-PDE), which had lost its sensitivity to Ca2+-calmodulin, was inhibited by various calmodulin antagonists, trifluoperazine, chlorpromazine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and aminoalkyl chain analogues of W-7 (A-3, A-4, A-5, I-240, A-6, A-7). These inhibitory effects were less than those on calmodulin-activated Ca2+-PDE. The ability of these compounds to inhibit trypsin-treated Ca2+-PDE correlated well with the inhibitory effect on calmodulin-activated Ca2+-PDE. W-7 inhibited trypsin-treated Ca2+-PDE in a competitive fashion with respect to cyclic GMP and the Ki value was 300 microM. The inhibition of trypsin-treated Ca2+-PDE by W-7 (300 microM) or A-7 (100 microM) was overcome by the addition of excess calmodulin. Trypsin-treated Ca2+-PDE can bind to W-7-coupled cyanogen bromide-activated Sepharose 4B in the presence of 1 mM EGTA. These results suggest that Ca2+-PDE possesses a binding site for calmodulin antagonists and that the binding site for these antagonists on this enzyme may be structurally similar to the binding site on calmodulin itself.

N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, a calmodulin antagonist, inhibits cell proliferation.[Pubmed:6945588]

Proc Natl Acad Sci U S A. 1981 Jul;78(7):4354-7.

N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and its derivatives are putative calmodulin antagonists that bind to calmodulin and inhibit Ca2+/calmodulin-regulated enzyme activities. Autoradiographic studies using tritiated W-7 showed that this compound penetrates the cell membrane, is distributed mainly in the cytoplasm, and inhibits proliferation of Chinese hamster ovary K1 (CHO-K1) cells. Cytoplasmic [3H]W-7 was excluded completely within 6 hr after removal of [3H]W-7 from the culture medium. N-(6-aminohexyl)-1-naphthalenesulfonamide, an analogue of W-7 that interacts only weakly with calmodulin, proved to be a much weaker inhibitor of cell proliferation. CHO-K1 cells were synchronized by shaking during mitosis and then released into the cell cycle in the presence of 25 microM W-7 or 2.5 mM thymidine for 12 hr. Cell division was observed approximately 6 hr later. The results suggest that the effect of W-7 on cell proliferation might be through selective inhibition of the G1/S boundary phase, which is similar to the effect of excess thymidine. This pharmacological demonstration that cytoplasmic calmodulin is involved in cell proliferation is significant; W-7 and its derivatives may be useful tools for research on calmodulin and cell biology-related studies.

Hydrophobic regions function in calmodulin-enzyme(s) interactions.[Pubmed:6254958]

J Biol Chem. 1980 Dec 10;255(23):11078-80.

Certain naturally occurring lipids (phosphatidylinositol, phosphatidylserine, arachidonic acid) and sodium dodecyl sulfate activate at least two calmodulin-dependent enzymes, bovine brain 3':5'-cyclic nucleotide phosphodiesterase and chicken gizzard myosin light chain kinase in the absence of Ca2+. 2-p-Toluidinyl-naphthalene-6-sulfonate (TNS), which is often used as a probe for hydrophobic groups of proteins, inhibits these two calmodulin-dependent enzymes. Kinetic analysis of inhibition of chicken gizzard myosin kinase by TNS revealed a competitive fashion against calmodulin-induced activation. The interaction between TNS and purified bovine brain calmodulin as demonstrated in the appearance of TNS fluorescence in the presence of 3 microM or more of calcium ion was not observed in the presence of 2 mM EGTA. This suggests that TNS is able to bind to calmodulin in the presence of Ca2+. Moreover, a calmodulin-interacting agent N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide suppressed the TNS fluorescence induced by complex formation with calmodulin in the presence of Ca2+. These results suggest that when Ca2+ binds to the high affinity sites of calmodulin, it induces a conformational change which exposes hydrophobic groups, and the calmodulin is then capable of activating calmodulin-dependent enzymes. We propose that hydrophobic properties of Ca2+-calmodulin are important for the activation of Ca2+-calmodulin-dependent enzymes.