An unpredicted aggregation-critical region of the actin-polymerizing protein TRIOBP-1/Tara, determined by elucidation of its domain structure

Nicholas J Bradshaw,Antony S.K Yerabham,Rita Marreiros,Tao Zhang,Luitgard Nagel-Steger,Carsten Korth

doi:10.1074/jbc.m116.767939

Nicholas J Bradshaw, Antony S.K Yerabham + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m116.767939

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Abstract

Aggregation of specific proteins in the brains of patients with chronic mental illness as a result of disruptions in proteostasis is an emerging theme in the study of schizophrenia in particular. Proteins including DISC1 (disrupted in schizophrenia 1) and dysbindin-1B are found in insoluble forms within brain homogenates from such patients. We recently identified TRIOBP-1 (Trio-binding protein 1, also known as Tara) to be another such protein through an epitope discovery and proteomics approach by comparing post-mortem brain material from schizophrenia patients and control individuals. We hypothesized that this was likely to occur as a result of a specific subcellular process and that it, therefore, should be possible to identify a region of the TRIOBP-1 protein that is essential for its aggregation to occur. Here, we probe the domain organization of TRIOBP-1, finding it to possess two distinct coiled-coil domains: the central and C-terminal domains. The central domain inhibits the depolymerization of F-actin and is also responsible for oligomerization of TRIOBP-1. Along with an N-terminal pleckstrin homology domain, the central domain affects neurite outgrowth. In neuroblastoma cells it was found that the aggregation propensity of TRIOBP-1 arises from its central domain, with a short "linker" region narrowed to within amino acids 324-348, between its first two coiled coils, as essential for the formation of TRIOBP-1 aggregates. TRIOBP-1 aggregation, therefore, appears to occur through one or more specific cellular mechanisms, which therefore have the potential to be of physiological relevance for the biological process underlying the development of chronic mental illness.

Highlights

Many chronic neurodegenerative conditions can be characterized by the presence of insoluble aggregates of specific proteins as evidence for aberrant proteostasis
The concept that aberrant proteostasis may exist in psychiatric illness is an emerging one, with TRIOBP-1 being a potential example of such a protein, having been identified via a hypothesis-free affinity proteomics approach using brain samples of patients with schizophrenia [8]
We have demonstrated that a specific region of TRIOBP-1, bounded by aa 324 –348, is an absolute requirement for its aggregation, indicating that it is likely to occur through a specific physiological process as opposed to the random aggregation of naturally sticky proteins

Summary

To whom correspondence may be addressed

Institut für Neuropathologie, Heinrich Heine Universität Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany. We performed an antibody-based screen for proteins that form insoluble aggregates in the brains of patients with schizophrenia [6] This was based on the hypothesis that disrupted protein homeostasis in post-mitotic neurons is likely to characterize subtypes of chronic mental illness [7]. In this manner, an antibody against TRIOBP-1 was found to show specificity for the pooled purified insoluble protein fractions of post-mortem brain samples from schizophrenia patients compared with an equivalent preparation prepared from brain samples of control individuals [8]. Investigate the domain structure of TRIOBP-1 and establish that such an aggregationcritical region exists that can be narrowed down to a stretch of just 25 amino acids (aa), strongly supporting the idea that a specific mechanism exists by which TRIOBP-1 forms insoluble aggregates

Results

Discussion

Experimental procedures