Staurosporine

The bacterium Streptomyces staurosporeus

Staurosporine, an alkaloid produced in Streptomyces staurospores originally as an antifungal agent, is an inhibitor of a broad spectrum of protein kinases, including protein kinase C (PKC), Camp-dependent protein kinase (PKA), phosphorylase kinase, ribosomal protein S6 kinase, epidermal growth factor receptor (EGF-R) kinase and Ca²⁺/calmodulin-dependent protein kinase II (Ca/CaM PKII). The inhibition potency is strongest for PKC (IC50 = 2.7 nM) but several-fold lower for other protein kinases. Staurosporine exhibits a strong cytotoxicity to some mammalian tumor cell lines, induces cell apoptosis, and arrests fission yeast cell elongation specifically at a stage immediately after cell division.

Reference

Takashi Toda, Mizuki Shimanuki, and Mitsuhiro Yanagida. Fission yeast genes that confer resistance to staurosporine encode an AP-1-like transcription factor and a protein kinase related to the mammalian ERK1/MAP2 and budding yeast FUS3 and KSS1 kinases. Genes Dev. 1991 5: 60-73

Michelle M. Hill, Mirjana Andelkovic, Derek P. Brazil, Stefano Ferrari, Doriano Fabbro, and Brian A. Hemmings. Insulin-stimulated protein kinase B phosphorylation on Ser-473 is independent of its activity and occurs through a Staurosporine-insensitive kinase. J. Biol. Chem 2001, 276: 25643-25646.

Flavio Meggio, Arianna Donella Deana, Maria Ruzzene, Anna M. Brunati, Luca Cesaro, Barbara Guerra, Thomas Meyer, Helmut Mett, Doriano Fabbro, Pascal Furet, Grazyna Dobrowolska, and Lorenzo A. Pinna. Different susceptibility of protein kinases to staurosporine inhibition kinetic studies and molecular bases for the resistance of protein kinase CK2. Eur. J. Biochem. 234, 317-322 (1995)

Reactive Oxygen Species Evoked by Potassium Deprivation and Staurosporine Inactivate Akt and Induce the Expression of TXNIP in Cerebellar Granule Neurons.[Pubmed:28367274]

Oxid Med Cell Longev. 2017;2017:8930406.

The reactive oxygen species (ROS) play a critical role in neuronal apoptosis; however, the mechanisms are not well understood. It has been shown that thioredoxin-interacting protein (TXNIP) overexpression renders cells more susceptible to oxidative stress and promotes apoptosis and that the activation of PI3K/Akt pathway leads to a downregulation of TXNIP. Here, we evaluated the role of ROS in the regulation of Akt activity and the subsequent regulation of the TXNIP expression in a model of apoptotic death of cerebellar granule neurons (CGN). We observed that two apoptotic conditions that generate ROS at short times led to an increase in the expression of TXNIP in a time-dependent manner; antioxidants significantly reduced this expression. Also, H2O2 caused an increase in TXNIP expression. Moreover, apoptotic conditions induced inactivation of Akt in a time-dependent manner similar to TXNIP expression and H2O2 treatment led to Akt inactivation. Besides, the pharmacological inhibition of Akt increases TXNIP expression and induces CGN cell death. Together, these results suggest that ROS promote neuronal apoptosis through the Akt-TXNIP signaling pathway, supporting the idea that the PI3K/Akt pathway regulates the TXNIP expression. This study highlights the potential importance of this mechanism in neuronal death.

Staurosporine suppresses survival of HepG2 cancer cells through Omi/HtrA2-mediated inhibition of PI3K/Akt signaling pathway.[Pubmed:28349827]

Tumour Biol. 2017 Mar;39(3):1010428317694317.

Staurosporine, which is an inhibitor of a broad spectrum of protein kinases, has shown cytotoxicity on several human cancer cells. However, the underlying mechanism is not well understood. In this study, we examined whether and how this compound has an inhibitory action on phosphatidylinositol 3-kinase (PI3K)/Akt pathway in vitro using HepG2 human hepatocellular carcinoma cell line. Cell viability and apoptosis were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) assay, respectively. Glutathione S-transferase (GST) pull-down assay and co-immunoprecipitation were performed to detect protein-protein interactions. Small interfering RNA (siRNA) was used to silence the expression of targeted protein. We found that Staurosporine significantly decreased cell viability and increased cell apoptosis in a concentration- and time-dependent manner in HepG2 cancer cells, along with the decreased expressions of PDK1 protein and Akt phosphorylation. Staurosporine was also found to enhance Omi/HtrA2 release from mitochondria. Furthermore, Omi/HtrA2 directly bound to PDK1. Pharmacological and genetic inhibition of Omi/HtrA2 restored protein levels of PDK1 and protected HepG2 cancer cells from Staurosporine-induced cell death. In addition, Staurosporine was found to activate autophagy. However, inhibition of autophagy exacerbated cell death under concomitant treatment with Staurosporine. Taken together, our results indicate that Staurosporine induced cytotoxicity response by inhibiting PI3K/Akt signaling pathway through Omi/HtrA2-mediated PDK1 degradation, and the process provides a novel mechanism by which Staurosporine produces its therapeutic effects.

Staurosporine Induces Filamentation in the Human Fungal Pathogen Candida albicans via Signaling through Cyr1 and Protein Kinase A.[Pubmed:28261668]

mSphere. 2017 Mar 1;2(2). pii: mSphere00056-17.

Protein kinases are key regulators of signal transduction pathways that participate in diverse cellular processes. In fungal pathogens, kinases regulate signaling pathways that govern drug resistance, stress adaptation, and pathogenesis. The impact of kinases on the fungal regulatory circuitry has recently garnered considerable attention in the opportunistic fungal pathogen Candida albicans, which is a leading cause of human morbidity and mortality. Complex regulatory circuitry governs the C. albicans morphogenetic transition between yeast and filamentous growth, which is a key virulence trait. Here, we report that Staurosporine, a promiscuous kinase inhibitor that abrogates fungal drug resistance, also influences C. albicans morphogenesis by inducing filamentation in the absence of any other inducing cue. We further establish that Staurosporine exerts its effect via the adenylyl cyclase Cyr1 and the cyclic AMP (cAMP)-dependent protein kinase A (PKA). Strikingly, filamentation induced by Staurosporine does not require the known upstream regulators of Cyr1, Ras1 or Pkc1, or effectors downstream of PKA, including Efg1. We further demonstrate that Cyr1 is capable of activating PKA to enable filamentation in response to Staurosporine through a mechanism that does not require degradation of the transcriptional repressor Nrg1. We establish that Staurosporine-induced filamentation is accompanied by a defect in septin ring formation, implicating cell cycle kinases as potential Staurosporine targets underpinning this cellular response. Thus, we establish Staurosporine as a chemical probe to elucidate the architecture of cellular signaling governing fungal morphogenesis and highlight the existence of novel circuitry through which the Cyr1 and PKA govern a key virulence trait. IMPORTANCE The impact of fungal pathogens on human health is devastating. One of the most pervasive fungal pathogens is Candida albicans, which kills ~40% of people suffering from bloodstream infections. Treatment of these infections is extremely difficult, as fungi are closely related to humans, and there are limited drugs that kill the fungus without host toxicity. The capacity of C. albicans to transition between yeast and filamentous forms is a key virulence trait. Thus, understanding the genetic pathways that regulate morphogenesis could provide novel therapeutic targets to treat C. albicans infections. Here, we establish the small molecule Staurosporine as an inducer of filamentous growth. We unveil distinct regulatory circuitry required for Staurosporine-induced filamentation that appears to be unique to this filament-inducing cue. Thus, this work highlights the fact that small molecules, such as Staurosporine, can improve our understanding of the pathways required for key virulence programs, which may lead to the development of novel therapeutics.

Stathmin decreases cholangiocarcinoma cell line sensitivity to staurosporine-triggered apoptosis via the induction of ERK and Akt signaling.[Pubmed:28178656]

Oncotarget. 2017 Feb 28;8(9):15775-15788.

Cholangiocarcinoma is a rare, but highly fatal malignancy. However, the intrinsic mechanism involved in its tumorigenesis remains obscure. An urgent need remains for a promising target for cholangiocarcinoma biological therapies. Based on comparative proteomical technologies, we found 253 and 231 different spots in gallbladder tumor cell lines and cholangiocarcinoma cell lines, respectively, relative to non-malignant cells. Using Mass Spectrometry (MS) and database searching, we chose seven differentially expressed proteins. High Stathmin expression was found in both cholangiocarcinoma and gallbladder carcinoma cells. Stathmin expression was validated using immunohistochemistry and western blot in cholangiocarcinoma tissue samples and peritumoral tissue. It was further revealed that high Stathmin expression was associated with the repression of Staurosporine-induced apoptosis in the cholangiocarcinoma cell. Moreover, we found that Stathmin promoted cancer cell proliferation and inhibited its apoptosis through protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) signaling. Integrin, beta1 appears to serve as a partner of Stathmin induction of ERK and Akt signaling by inhibiting apoptosis in the cholangiocarcinoma cell. Understanding the regulation of anti-apoptosis effect by Stathmin might provide new insight into how to overcome therapeutic resistance in cholangiocarcinoma.

Staurosporine: an effective inhibitor for Ca2+/calmodulin-dependent protein kinase II.[Pubmed:1846174]

J Neurochem. 1991 Jan;56(1):294-8.

We investigated the effect of Staurosporine on Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) purified from rat brain. (a) Staurosporine (10-100 nM) inhibited the activity of CaM kinase II. The half-maximal and maximal inhibitory concentrations were 20 and 100 nM, respectively. (b) The inhibition with Staurosporine was of the noncompetitive type with respect to ATP, calmodulin, and phosphate acceptor (beta-casein). (c) Staurosporine suppressed the auto-phosphorylation of alpha- and beta-subunits of CaM kinase II at concentrations similar to those at which the enzyme activity was inhibited. (d) Staurosporine also attenuated the Ca2+/calmodulin-independent activity of the autophosphorylated CaM kinase II. These results suggest that Staurosporine inhibits CaM kinase II by interacting with the catalytic domain, distinct from the ATP-binding site or substrate-binding site, of the enzyme and that Staurosporine is an effective inhibitor for CaM kinase II in the cell system.

Staurosporine, a potent inhibitor of phospholipid/Ca++dependent protein kinase.[Pubmed:3457562]

Biochem Biophys Res Commun. 1986 Mar 13;135(2):397-402.

Staurosporine, microbial alkaloid which has been known to have antifungal activity was found to inhibit markedly phospholipid/Ca++dependent protein kinase (protein kinase C) from rat brain, with an IC50 value of 2.7 nM. However, it had little effect on the binding of 3H-phorbol-12, 13-dibutyrate (PDBu) to protein kinase C. The inhibition of protein kinase C was not competitive with phospholipid. This compound also showed the strong cytotoxic effect on the growth of HeLa S3 cells, with an IC50 value of 4 X 10(-12)M under the condition of 72 hr-exposure.

Staurosporine is a potent and non-selective inhibitor of protein kinases with IC50s of 6 nM, 15 nM, 2 nM, and 3 nM for PKC, PKA, c-Fgr, and Phosphorylase kinase respectively.

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