The versatile molecular complex component LC8 promotes several distinct steps of flagellar assembly

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• The LC8 protein is found in various molecular complexes, but its precise function is not fully understood.
• The radial spoke (RS) complex is crucial for flagellar function, and LC8 is known to be a subunit.

Purpose of the Study:

• To elucidate the role of LC8 in the assembly of the radial spoke complex within Chlamydomonas flagella.
• To investigate the interaction between LC8 and RS protein 3 (RSP3) during axoneme assembly.

Main Methods:

• Analysis of LC8 presence in RS precursors and mature RS complexes.
• Biochemical assays to study the binding of LC8 dimers to RSP3 N-terminal fragments.
• Investigating the effect of perturbing RSP3's LC8-binding sites on flagellar assembly and function.

Main Results:

• LC8 was detected in mature RS complexes but not in RS precursors.
• LC8 dimers bind to the N-terminal region of RSP3, enhancing its binding to axonemes.
• Disruption of LC8-binding sites on RSP3 led to asynchronous flagella, reduced RSP3 phosphorylation, and impaired RS-axoneme association.

Conclusions:

• LC8 binding to RSP3 in RS precursors at the flagellar tip is proposed to initiate phosphorylation, stalk base formation, and axoneme targeting.
• This mechanism provides new insights into the assembly of LC8-containing complexes and the intricate process of axoneme formation.