N-Terminal Processing and Modification of Ciliary Dyneins

Area of Science:

• Cell Biology
• Molecular Motors
• Protein Biochemistry

Background:

• Axonemal dyneins are essential multi-subunit microtubule motors driving ciliary motility.
• Their assembly involves numerous cytosolic factors and complex post-translational modifications.
• N-terminal acetylation and processing can regulate protein stability, interactions, and degradation via the N-end rule pathway.

Purpose of the Study:

• To investigate the N-terminal processing and acetylation of axonemal dynein heavy chains in Chlamydomonas.
• To identify the specific N-terminal acetylase complexes involved in dynein subunit maturation.
• To understand how N-terminal modifications influence dynein complex assembly and stoichiometry.

Main Methods:

• Mass spectrometry analysis of Chlamydomonas cilia and purified dynein heavy chains.
• Electrophoretic purification of dynein heavy chains.
• Identification and characterization of N-terminal acetylase complexes.

Main Results:

• Four distinct classes of dynein heavy chain processing pathways were identified based on N-terminal acetylation.
• Two specific N-terminal acetyltransferases were found to be involved in dynein heavy chain processing.
• One dynein complex component undergoes processing to an unmodified Pro residue, potentially regulating cytosolic stoichiometry.
• Methionine aminopeptidase activity was found to be essential for one processing pathway.

Conclusions:

• N-terminal processing and acetylation represent a significant regulatory layer in axonemal dynein biogenesis.
• Specific N-terminal modifications fine-tune the assembly and stability of dynein motor complexes.
• This study reveals novel mechanisms controlling the formation of functional dynein motors for ciliary function.