Cytoskeleton, Inc. is currently expanding its drug screening product lines and services. You can get updated information about the latest drug screens available from Cytoskeleton, Inc. by calling the Technical Support at 303-322-2254. At present, Cytoskeleton, Inc. is offering tubulin based screens for the detection of novel therapeutics. Four types of tubulin are commonly used for this purpose
1. Highly purified tubulin >99% pure from bovine brain (Cat. # TL238),
2. HTS-tubulin which is >97% pure (Cat. # HTS02) and
3. MAP-rich tubulin 70% pure from bovine brain (Cat. # ML113).
4. Cancer cell tubulin from human cancer cell lines (Cat. # H001 and H005)
Although TL238 is the best choice for tubulin interacting drugs, HTS02 and ML113 are less expensive and probably good for initial screening. It must be remembered that compounds may interact with the MAPs in this preparation rather than the tubulin. The cancer cell tubulins, from HeLa cells (Cat. # H001) and MCF-7 cells (Cat. H005), allow for testing drug interactions with tubulins from actively dividing human cancer cell lines, likely reflecting a more relevant target for cancer therapeutics. See each product page for examples differences in drug interaction between cancer cell tubulins and bovine brain tubulin. Below is a more detailed description of the various tubulin screens available from Cytoskeleton, Inc. Please inquire if you have any further questions tservice@cytoskeleton.com. See also Tubulin Polymerization Assay Kits (Cat. # BK006 and BK011).
Other CytoDYNAMIX™ Screens are described on the HTS page
The Microtubule Network As A Target For Therapeutic Agents:
Microtubules are formed by the polymerization of the heterodimeric protein tubulin. There are at least 14 tubulin isotypes in higher eukaryotes, some of which are expressed in a tissue specific manner. Observation of microtubule polymerization in vitro led to the discovery that microtubules are intrinsically dynamic structures that are continually in a state of flux. This property, termed dynamic instability, was subsequently shown to occur in vivo. Importantly, microtubule dynamics have been shown to alter during the cell cycle and are often very different between cell types. The dynamic nature of microtubules is now recognized to be essential for them to mediate their various cellular functions. Agents that can selectively disrupt microtubule dynamics, either by targeting a specific tubulin isotype or a particular stage of cell division would be predicted to have great therapeutic value. Several highly promising anti-cancer drugs (which exploit the difference in microtubule dynamics between rapidly dividing (cancerous) and predominantly non-dividing (most normal cell populations) cells have been developed that act by disrupting microtubule dynamics. These include microtubule de-stabilizing drugs such as vinblastine and the stabilizing drug taxol.
Screening Services Available:
Cytoskeleton can perform many microtubule and tubulin based assays to screen for anti-microtubule drugs and to quantitate biological activity. We have many years experience in the design and implementation of such screens which have resulted in several novel microtubule based drugs. Our service includes a comprehensive written assessment of each test compound's activity on tubulin and microtubules. The assays vary in complexity from a simple exploratory polymerization assay using the "standard" bovine brain tubulin to a full mechanistic appraisal of a compound's activity using other types of tubulin, such as those isolated from other species e.g. yeast, fungi, plant and human (including tumor cell line) tubulins. We can design and/or accommodate any type or scale of assay, please inquire for your requirements. We offer very competitive rates with discounts available for multiple compound screens.
Tubulin and Microtubules: The System:
An in vitro microtubule assay is defined as a system to assess the interaction of putative or known anti-microtubule drugs with their target. The interaction can affect the extent of polymerization either by stabilizing microtubules as is the case for taxol, or, by destabilizing microtubules as for nocodozole. There are many anti-microtubule compounds in everyday use, for example human cancer therapy (vincristine, podophyllatoxin) or fungicide (benomyl).
Polymerization assay: As discussed before in the section on tubulin protein, microtubules are composed of thirteen protofilaments arranged in a cylindrical fashion. The protofilaments are composed of polymerized tubulin subunits. Tubulin polymerization is a complex process that is still not fully understood. However, there are three defined stages of tubulin polymerization, these are nucleation, elongation and steady state. All compounds that interact with tubulin and microtubules affect one or more stage of polymerization, therefore, by measuring polymerization very accurately, we can identify all compounds which interact with tubulin or microtubules. Accurate measurement of polymerization can be achieved by optical absorbance measurements, this forms the basis of the recommended preliminary drug screen.
Other microtubule based assays: To further understand the biological potency and the mechanistic basis of an anti-microtubule compound there are a variety of microtubule assays to perform. For example, you could measure the Inhibitory Concentration for 50% polymer formation (IC50), this value can be cross referenced to other drugs to compare potency. Alternatively, you could measure the activity of the compound on microtubule depolymeriztion, thus elucidating whether the compound binds to and stabilizes microtubules. These assays provide more information to improve the drug design by a rational approach.
Quotation for services:
Cytoskeleton, Inc. will be pleased to give a quotation on any service required for compound screening using microtubule based assays. Please contact our offices at 303-322-2254 and ask for Technical Support or e-mail tservice@cytoskeleton.com.
Other CytoDYNAMIX Screens are described on the HTS page
