Distinct localization of a beta-tubulin epitope in the Tetrahymena thermophila and Paramecium caudatum cortex

The function of the ATG8 in the cilia and cortical microtubule maintenance of Euplotes amieti

Autophagy regulates the formation of primary cilia, which in turn affects autophagy. The relationship between autophagy and cilia is known to be bidirectional although the specific mechanisms involved have yet to be elucidated. In this study, we found for the first time that ATG8 protein localizes in the basal body of the dorsal kineties and the base of the ventral cirri in Euplotes amieti. ATG8 protein maintains the structural integrity of cilia and plays a role in the construction of the cortical ciliature and microtubule cytoskeleton associated with cilia. ATG8 gene interference leads to the degradation of IFT88, the transport protein in cilia, thus inhibiting the generation of cilia, and affecting the swing of cilia. This influences the swimming speed and cilia pattern, leading to death in Euplotes amieti.

Exposure of beta-tubulin regions defined by antibodies on an Arabidopsis thaliana microtubule protofilament model and in the cells

BACKGROUND

The function of the cortical microtubules, composed of alphabeta-tubulin heterodimers, is linked to their organizational state which is subject to spatial and temporal modulation by environmental cues. The role of tubulin posttranslational modifications in these processes is largely unknown. Although antibodies against small tubulin regions represent useful tool for studying molecular configuration of microtubules, data on the exposure of tubulin epitopes on plant microtubules are still limited.

RESULTS

Using homology modeling we have generated an Arabidopsis thaliana microtubule protofilament model that served for the prediction of surface exposure of five beta-tubulin epitopes as well as tyrosine residues. Peptide scans newly disclosed the position of epitopes detected by antibodies 18D6 (beta1-10), TUB2.1 (beta426-435) and TU-14 (beta436-445). Experimental verification of the results by immunofluorescence microscopy revealed that the exposure of epitopes depended on the mode of fixation. Moreover, homology modeling showed that only tyrosines in the C-terminal region of beta-tubulins (behind beta425) were exposed on the microtubule external side. Immunofluorescence microscopy revealed tyrosine phosphorylation of microtubules in plant cells, implying that beta-tubulins could be one of the targets for tyrosine kinases.

CONCLUSIONS

We predicted surface exposure of five beta-tubulin epitopes, as well as tyrosine residues, on the surface of A. thaliana microtubule protofilament model, and validated the obtained results by immunofluorescence microscopy on cortical microtubules in cells.The results suggest that prediction of epitope exposure on microtubules by means of homology modeling combined with site-directed antibodies can contribute to a better understanding of the interactions of plant microtubules with associated proteins.

Expression of beta-tubulin epitope in human sperm with pathological spermiogram

OBJECTIVE

To determine the location of the corresponding epitope on the tubulin molecule and to find any differences in its exposition in human sperm with normal and pathological spermiograms. The mature spermatozoon exhibits extraordinary structural compartmentalization that is related to the presence of cytoskeletal proteins and has a functional role in connection with fertilization and motility. Previously, we have shown that anti-beta-tubulin antibody TU-12 provided an unexpectedly strong reaction in human and boar sperm head.

DESIGN

A retrospective study.

SETTING

Academic research laboratories and private IVF center.

PATIENT(S)

One hundred thirteen men participating in the IVF program.

INTERVENTION(S)

Sperm were divided into five categories: normozoospermia, oligozoospermia, asthenozoospermia, teratozoospermia, and asthenoteratozoospermia. Well-characterized monoclonal antibodies were applied for monitoring tubulin epitope distributions in pathological spermatozoa.

MAIN OUTCOME MEASURE(S)

Qualitative and quantitative detection of tubulin.

RESULT(S)

TU-12 epitope was located in the beta-tubulin region beta 426-435. Immunoblotting revealed differences in the amount of tubulin among men with normozoospermia and pathological spermiogram. Striking differences were observed in the exposition of TU-12 epitope in heads of normal and pathological spermatozoa.

CONCLUSION(S)

The results suggest that tubulin epitopes could be useful biomarkers of the pathological sperm state.