Yuna Ayala, Ph.D.

Yuna Ayala, Ph.D.
Associate Professor & Vice Chair

Studies on RNA binding protein function in eukaryotic mRNA processing and neurodegenerative diseases.

Office: DRC 523
Voice: (314) 977-9247

Research Interests

The regulation of pre-mRNA processing, critical in the control of gene function and often linked to human disease, is mediated through the interaction between mRNA and protein partners. The TAR DNA binding protein (TDP-43) is an essential RNA binding protein whose dysfunction and aggregation are tightly associated with neurodegenerative disorders, i.e., amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease, and frontotemporal lobar degeneration (FTLD). We investigate the cellular function and molecular structure of RNA binding proteins, such as TDP-43, to understand basic mechanisms of RNA processing and pathogenesis.
Research Highlights
TDP-43 Function and Aggregation
Ayala Figure 1

The main questions addressed in our work:

  • How is TDP-43 homeostasis regulated under non-pathological conditions?
  • What factors trigger TDP-43 aggregation?
  • What is the function of TDP-43 relevant to ALS and FTLD pathogenesis?
TDP-43 Phosphorylation
Ayala Figure 2

We found a novel dual phosphorylation site in TDP-43, p-T153/Y155, which is activated in response to proteotoxic stress, i.e., heat shock response.

  • p-T153/Y155 is specifically phosphorylated by MEK, the central kinase in the MAPK/ERK pathway.
  • p-T153/Y155 is recruited to the nucleolar compartment under normal conditions, and is upregulated after heat shock.
  • Phosphorylation is not associated with aggregates, autophagy, or degradation. Instead, p-T153/Y155 remains soluble under conditions of proteotoxic stress.

Heat shock-induced phosphorylation of TAR DNA-binding Protein 43 (TDP-43) by MAPK/ERK kinase regulates TDP-43 function. Li W, et al., J. Biol. Chem. 292(12):5089-5100, 2017 (PMID: 28167528).

TDP-43 Self-Assembly and Aggregation
Ayala Figure 3

TDP-43, similar to other RNA binding proteins linked to ALS and FTLD, self-assembles and binds other ribonucleoproteins to form RNA-protein rich granules in cells (e.g., nucleolus, Cajal bodies, stress granules, etc.). These complexes are aggregation prone and, under certain conditions, may form pathological inclusions.

TDP-43 Aggregation and Intracellular Propagation Assays
Ayala Figure 4

We study the process of aggregation using purified recombinant TDP-43. Aggregate complexes formed over time are analyzed by semi-denaturing SDS agarose gel electrophoresis (SDS-AGE) (French RL, et al. Proc. Natl. Acad. Sci. USA, in review).

Using these assays we found that:

  • High molecular weight fibrillar aggregates are preceded by oligomeric complexes.
  • ALS-linked mutations, A315T and M337V, dramatically accelerate aggregation.
  • Our cellular reporter for TDP-43 aggregation shows that rTDP-43 aggregates (labeled green) seed and propagate intracellular aggregates (labeled red). This propagation is also increased by the ALS-linked mutations as seen by counting the aggregate-positive cells at 48 hours or 6 days after treatment.

Recent Publications

Department of Biochemistry and Molecular Biology