Electrophoretic resolution of tubulin and tektin subunits by differential interaction with long-chain alkyl sulfates

Purification and Localization of Intraflagellar Transport Particles and Polypeptides

The growth and maintenance of almost all cilia and flagella are dependent on the proper functioning of the process of intraflagellar transport (IFT). This includes the primary cilia of most human cells that are in the Go phase of the cell cycle. The model system for the study of IFT is the flagella of the biflagellate green alga Chlamydomonas. It is in this organism that IFT was first discovered, and genetic data from a Chlamydomonas mutant first linked the process of IFT to polycystic kidney disease in humans. The information provided in this chapter addresses procedures to purify IFT particles from flagella and localize these particles, and their associated motor proteins, in flagella using light and electron microscopic approaches.

High-resolution separation of tubulin monomers on polyacrylamide minigels

High-resolution separation of alpha- and beta-tubulin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) on minigels can be performed rapidly using simple modifications of the standard Laemmli procedure. Separation of the subunits can be observed even in high-protein loads (up to 40microg of protein).

Purification and localization of intraflagellar transport particles and polypeptides

The growth and maintenance of almost all cilia and flagella are dependent on the proper functioning of the process of intraflagellar transport (IFT). This includes the primary cilia of most cells in humans that are in interphase or the G(o) phase of the cell cycle. The model system for the study of IFT is the flagella of the bi-flagellate green alga Chlamydomonas. It is in this organism that IFT was first discovered, and genetic data from a Chlamydomonas mutant first linked the process of IFT to polycystic kidney disease in humans. The information given in this chapter addresses procedures to purify IFT particles from flagella and localize these particles, and their associated motor proteins, in flagella using light and electron microscopic approaches.

Methods in tubulin proteomics

New analytical methods are needed for the successful outcome of experiments aimed at characterizing mechanisms of microtubule dynamics and at understanding the effects of drugs on microtubules. The identification of tubulin isotypes and of regions of the microtubule involved in drug interactions has been advanced by proteomic methodologies. The diversity of tubulin sequences and posttranslational modifications (PTMs) can generate a complex mixture of heterodimers with unique molecular dynamics driving specific functions. Mass spectrometry (MS)-based approaches have been developed, and in combination with chromatographic and/or electrophoretic separation of tubulin polypeptides or peptides, they have contributed to our understanding of tubulin proteomics. We present protocols that we have used for the analysis of tubulin isotypes and PTMs present in tubulin isolated from cells in culture or tissues and for the identification of tubulin regions altered by microtubule-stabilizing agents. Tubulin proteomics complements structural and computer modeling information for a high-resolution view of microtubule dynamics and its alteration by drugs. These methodologies will help in providing insights into tubulin isotype-specific functions and in the design of drugs targeting either all tubulin heterodimers indiscriminately or only those containing specific isotypes.

Plasma membrane tubulin

The association of tubulin with the plasma membrane comprises multiple levels of penetration into the bilayer: from integral membrane protein, to attachment via palmitoylation, to surface binding, and to microtubules attached by linker proteins to proteins in the membrane. Here we discuss the soundness and weaknesses of the chemical and biochemical evidence marshaled to support these associations, as well as the mechanisms by which tubulin or microtubules may regulate functions at the plasma membrane.

Characterization and functional analysis of cAMP response element modulator protein and activating transcription factor 2 (ATF2) isoforms in the human myometrium during pregnancy and labor: identification of a novel ATF2 species with potent transactivation properties

There is now extensive evidence to indicate that components of the cAMP signaling pathway are up-regulated in the human myometrium during pregnancy so as to potentiate the maintenance of uterine quiescence until term. In many tissue and cell types, increased signaling of the cAMP pathway results in profound changes in gene expression that are catalyzed via stimulation of PKA and activation of cAMP-dependent transcription factors that bind cAMP response elements (CREs) within the promoter regions of affected genes. In the myometrium, these CRE containing genes include beta2-adrenoceptor, cyclo-oxygenase 2, oxytocin receptor, and connexin-43. In preliminary investigations, we reported the differential expression of members of the cAMP bZIP protein family in the myometrium during pregnancy and labor. In this present study, we have now identified and functionally characterized these proteins with respect to myometrial gene expression. We report the identification of a 39,000 mol wt CRE response element modulator protein (CREM)tau2alpha protein having both transactivation and transrepressor properties whose expression is sequentially decreased in the myometrium during gestation and parturition. In contrast, expression of a myometrial 28,000 mol wt CREMalpha protein having only transrepressor actions progressively increased in the myometrium during pregnancy and labor. Similarly, we have isolated two ATF2 proteins of 60,000 and 28,000 mol wts, which represent full-length ATF2 and a novel small isoform of ATF2 that we have termed ATF2-small (ATF2-sm). These proteins are potent transactivators of gene expression and appear to be spatially expressed within the myometrium of the upper and lower uterine regions. The identification and functional characterization of these basic region/leucine zipper proteins in the myometrium may provide further insight into the molecular mechanisms regulating uterine activity during fetal maturation and parturition.