Therapeutic potential of inhibiting Bruton's tyrosine kinase, (BTK).

BTK (Bruton's tyrosine kinase) is a member of the TEC family of tyrosine kinases that plays a central but diverse modulatory role in various cellular processes. The unique role of BTK in a multitude of signaling pathways, its function as a dual regulator of apoptosis and its involvement in a number of developmental processes makes BTK a desirable target for potential anti-cancer, anti-inflammatory and anti-viral agents as well as other treatments. The biochemistry and signaling networks of BTK were well described in numerous detailed reviews written by members of our team and others before us. Therefore in this particular review we are going to concentrate on the possible practical application of previously obtained knowledge to specific diseases and disorders.

Members of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway are present and active in human sperm.

OBJECTIVE: To investigate whether components of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway are present and active in human sperm. DESIGN: Comparative study. SETTING: Reproductive biology department. PATIENT(S): Nine sperm donors. INTERVENTION(S): Sperm were exposed to interferon-alpha (IFN-alpha), IFN-gamma, interleukin-12 (IL-12), Ca2+ ionophore (A23187), or progesterone under capacitating conditions. MAIN OUTCOME MEASURE(S): Cell lysates prepared from sperm and Jurkat T-cell line were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the expression of JAKs (1-3 and TYK 2) and STATs (1-6) was examined by Western blot analysis. Effect of IFN-alpha, IFN-gamma, IL-12, A23187, or progesterone on sperm STAT 1 or STAT 4 phosphorylation was determined by phospho-STAT 1 antibody or antiphosphotyrosine (APT) Western blot analysis. Indirect immunofluorescence and confocal laser scanning microscopy was used to confirm the specific staining of anti-TYK 2, anti-STAT 1, and anti-STAT 4 antibodies. RESULT(S): By Western blot analysis, only antibodies to TYK 2 of the JAK family, and antibodies to STAT 1 and STAT 4 members of the STAT family specifically recognized protein bands corresponding to TYK 2, STAT 1, and STAT 4 described in other cell types. By confocal microscopy, antibodies to TYK 2 reacted with the sperm tail as well as the apical region of sperm head, whereas antibodies to STAT 1 and STAT 4 reacted with the apical region of the sperm head. Tyrosine phosphorylation of STAT 1 in capacitated sperm was enhanced by IFN-alpha and IFN-gamma, and that of STAT 4 was enhanced by IL-12. Both A23187 and progesterone markedly inhibited tyrosine phosphorylation of sperm STAT 4. CONCLUSION(S): Members of the JAK/STAT proteins, TYK 2, STAT 1, and STAT 4 are present and active in human sperm. The localization of STAT 1 and STAT 4 proteins to the apical region of the sperm head and their activation by IFN-alpha, IFN-gamma, or IL-12 implicate a role for sperm STAT proteins in fertilization. We hypothesize that sperm-derived phosphorylated STAT 1 and STAT 4 could contribute to the pool of transcription factors during sperm-oocyte fusion as well as transmit signal to the oocyte nucleus. Therefore, defects in sperm TYK 2 and STAT 1- or STAT 4-mediated signaling pathway may have relevance to male factor infertility.

Spongistatins as tubulin targeting agents.

Recently identified novel agents that disrupt tubulin polymerization include synthetic spiroketal pyrans (SPIKET) targeting the spongistatin binding site of b-tubulin. These agents exhibit anticancer activity by disrupting normal mitotic spindle assembly and cell division as well as inducing apoptosis. At nanomolar concentrations, the SPIKET compound SPIKET-P caused tubulin depolymerization in cell-free turbidity assays and exhibited potent cytotoxic activity against cancer cells as evidenced by destruction of microtubule organization, and prevention of mitotic spindle formation in human breast cancer cells. SPIKET compounds represent a new class of tubulin targeting agents that show promise as anti-cancer drugs.

Structure-based design of novel anticancer agents.

Recently identified agents that interact with cytoskeletal elements such as tubulin include synthetic spiroketal pyrans (SPIKET) and monotetrahydrofuran compounds (COBRA compounds). SPIKET compounds target the spongistatin binding site of beta-tubulin and COBRA compounds target a unique binding cavity on alpha-tubulin. At nanomolar concentrations, the SPIKET compound SPIKET-P causes tubulin depolymerization and exhibits potent cytotoxic activity against cancer cells. COBRA-1 inhibits GTP-induced tubulin polymerization. Treatment of human breast cancer and brain tumor cells with COBRA-1 caused destruction of microtubule organization and apoptosis. Other studies have identified some promising protein tyrosine kinase inhibitors as anti-cancer agents. These include EGFR inhibitors such as the quinazoline derivative WHI-P97 and the leflunomide metabolite analog LFM-A12. Both LFM-A12 and WHI-P97 inhibit the in vitro invasiveness of EGFR positive human breast cancer cells at micromolar concentrations and induce apoptotic cell death. Dimethoxyquinazoline compounds WHI-P131 and WHI-P154 inhibit tyrosine kinase JAK3 in leukemia cells. Of particular interest is WHI-P131, which inhibits JAK3 but not JAK1, JAK2, SYK, BTK, LYN, or IRK at concentrations as high as 350 microM. Studies of BTK inhibitors showed that the leflunomide metabolite analog LFM-A13 inhibited BTK in leukemia and lymphoma cells. Consistent with the anti-apoptotic function of BTK, treatment of leukemic cells with LFM-A13 enhanced their sensitivity to chemotherapy-induced apoptosis.

COBRA-1, a rationally-designed epoxy-THF containing compound with potent tubulin depolymerizing activity as a novel anticancer agent.

A novel mono-THF containing synthetic anticancer drug, COBRA-1, was designed for targeting a previously unrecognized unique narrow binding cavity on the surface of alpha-tubulin. COBRA-1 inhibited GTP-induced tubulin polymerization in cell-free tubulin turbidity assays. Treatment of human breast cancer and brain tumor (glioblastoma) cells with COBRA-1 caused destruction of microtubule organization and apoptosis. Like other microtubule-interfering agents, COBRA-1 activated the proapoptotic c-Jun N-terminal kinase (JNK) signal transduction pathway, as evidenced by rapid induction of c-jun expression.

A rationally designed anticancer drug targeting a unique binding cavity of tubulin.

A novel mono-THF containing synthetic anticancer drug (WHI-261) was designed for targeting a previously unrecognized unique narrow binding cavity on the surface of tubulin. The anti-cancer activity of WHI-261 was confirmed using MTT assays. The structure-based design, synthesis, and biological activity of WHI-261 are reported.

Structure-based design of a novel synthetic spiroketal pyran as a pharmacophore for the marine natural product spongistatin 1.

SPIKET-P, a novel synthetic spiroketal pyran, was rationally designed as a pharmocophore for the tubulin depolymerizing marine natural product Spongistatin 1. SPIKET-P was prepared from the commercially available benzyl (R)-(-)-glycidyl ether using a versatile 11-step synthetic scheme in a stereocontrolled fashion. At nanomolar concentrations, SPIKET-P caused tubulin depolymerization in cell-free turbidity assays and exhibited potent cytotoxic activity against cancer cells as evidenced by destruction of microtubule organization, and prevention of mitotic spindle formation in human breast cancer cells.

SPIKET and COBRA compounds as novel tubulin modulators with potent anticancer activity.

Agents that either promote or inhibit tubulin polymerization exhibit anticancer activity by disrupting normal mitotic spindle assembly and cell division as well as inducing apoptosis. Recently identified novel agents that target tubulin include synthetic spiroketal pyrans (SPIKET), targeting the spongistatin binding site of beta-tubulin, and COBRA compounds, targeting a unique binding cavity on alpha-tubulin. At nanomolar concentrations, the SPIKET compound SPIKET-P caused tubulin depolymerization in cell-free turbidity assays and exhibited potent cytotoxic activity against cancer cells as evidenced by destruction of microtubule organization, and prevention of mitotic spindle formation in human breast cancer cells. Molecular modeling studies predicted a high-affinity interaction of the first COBRA compounds, COBRA-0 and COBRA-1, with a unique hydrophobic binding site on alpha-tubulin located between the GTP/GDP binding site and the M-loop. Further studies showed that COBRA-1 inhibited GTP-induced tubulin polymerization in cell-free tubulin turbidity assays. Treatment of human breast cancer and brain tumor (glioblastoma) cells with COBRA-1 caused destruction of microtubule organization and apoptosis. COBRA-1 activated the pro-apoptotic c-Jun N-terminal kinase (JNK) signal transduction pathway. COBRA and SPIKET compounds represent two new classes of tubulin targeting agents that show promise as anticancer drugs.

Cytochrome c oxidase in Neurospora crassa contains myristic acid covalently linked to subunit 1.

Radiolabel from [3H]myristic acid was incorporated by Neurospora crassa into the core catalytic subunit 1 of cytochrome c oxidase (EC 1.9.3.1), as indicated by immunoprecipitation. This modification of the subunit, which was specific for myristic acid, represents an uncommon type of myristoylation through an amide linkage at an internal lysine, rather than an N-terminal glycine. The [3H]myristate, which was chemically recovered from the radiolabeled subunit peptide, modified an invariant Lys-324, based upon analyses of proteolysis products. This myristoylated lysine is found within one of the predicted transmembrane helices of subunit 1 and could contribute to the environment of the active site of the enzyme. The myristate was identified by mass spectrometry as a component of mature subunit 1 of a catalytically active, purified enzyme. To our knowledge, fatty acylation of a mitochondrially synthesized inner-membrane protein has not been reported previously.

Isolation, partial amino acid sequence, and cellular distribution of heat-shock protein hsp98 from Neurospora crassa.

Hsp98 is one of the most prominent proteins synthesized during the heat-shock response of Neurospora crassa. We purified hsp98 and determined the amino acid sequence of two overlapping peptides obtained by cyanogen bromide cleavage. This 28 amino acid sequence from hsp98 has 75% homology with a region of the ClpB protein of Escherichia coli and 86% homology to a 96-kDa protein of Trypanosoma brucei. It also has 71% homology to hsp104 of Saccharomyces cerevisiae. Hsp98 was enriched in the microsomal fraction of heat-shocked cells. Sucrose gradient analysis of this cellular fraction showed that the three major high molecular weight heat-shock proteins (hsp98, 83 and 67) were more concentrated in polyribosomes than in monoribosomes. Another newly synthesized protein, p28, was strongly enriched in monoribosomes. After dissociation of the polyribosomes into ribosomal subunits, the three major heat-shock proteins were shown to be localized preferentially in the large subunit. Whereas p28 was also strongly associated with the large ribosomal subunit, a newly synthesized protein of about 22 kDa was exclusively associated with the small subunit.