A Proline-Rich-Domain-Binding Single Domain Antibody Selectively Inhibits RNA-Induced Phase Separation of Tau

Area of Science:

• Biochemistry
• Cell Biology
• Neuroscience

Background:

• Phase separation drives biomolecular condensate formation, crucial for cellular organization like synaptic plasticity.
• The neuronal protein tau undergoes phase separation, influencing synaptic vesicle clustering and microtubule dynamics.
• While tau phase separation is induced by cofactors like PEG or RNA, its precise molecular mechanisms and domain-specific roles remain unclear.

Purpose of the Study:

• To explore the molecular mechanisms of tau phase separation in vitro.
• To investigate the domain-specific contributions to tau phase separation.
• To evaluate the effect of single-domain antibodies (VHHs) on tau phase separation.

Main Methods:

• Utilized eight single-domain antibodies (VHHs) targeting six distinct tau sequences.
• Employed various biophysical methods to assess VHH effects on tau phase separation.
• Applied Nuclear Magnetic Resonance (NMR) and Surface Plasmon Resonance (SPR) spectroscopies for binding analysis.

Main Results:

• VHHs targeting the microtubule binding domain enhanced tau phase separation with PEG induction.
• VHHs showed mixed effects with RNA induction: one promoted condensation, another (VHH B1-1) abolished it.
• VHH B1-1 specifically bound the proline-rich domain (PRD), and PRD peptide competition restored phase separation.

Conclusions:

• Domain-specific interactions significantly regulate tau phase separation.
• VHHs serve as selective probes to modulate tau phase separation and biomolecular condensates.
• Findings offer insights into tau's role in physiological and pathological contexts.