LIM domain protein TES changes its conformational states in different cellular compartments

The human TESTIN (TES) is a putative tumor suppressor and localizes to the cytoplasm as a component of focal adhesions and cell contacts. TES contains a PET domain in the NH₂-terminus and three tandem LIM domains in the COOH-terminus. It has been hypothesized that interactions between two termini of TES might lead to a “closed” conformational state of the protein. Here, we provide evidence for different conformational states of TES. We confirmed that the NH₂-terminus of TES can interact with its third LIM domain in the COOH-terminus by GST pull-down assays. In addition, antisera against the full-length or two truncations of TES were prepared to examine the relationship between the conformation and cellular distribution of the protein. We found that these antisera recognize different regions of TES and showed that TES is co-localised with the marker protein B23 in nucleolus, in addition to its localization in endoplasmic reticulum (ER). Furthermore, our co-immunoprecipitation (co-IP) analysis of TES and B23 demonstrated their co-existence in the same complex. Taken together, our results suggest that TES has different conformational states in different cellular compartments, and a “closed” conformational state of TES may be involved in nucleolar localization.