aPKC Cycles between Functionally Distinct PAR Protein Assemblies to Drive Cell Polarity

Area of Science:

• Cell Biology
• Developmental Biology
• Molecular Cell Biology

Background:

• The PAR protein network is crucial for establishing cell polarity in various animal cell types.
• Polarity establishment requires spatial activation of atypical protein kinase C (aPKC) in response to external cues.
• The Caenorhabditis elegans zygote serves as a model system for studying fundamental cell polarization mechanisms.

Purpose of the Study:

• To investigate the distinct mechanisms governing the localization and activation of aPKC within the PAR network.
• To understand how different protein assemblies contribute to the spatial regulation of aPKC during cell polarization.
• To elucidate the role of protein cycling between assemblies in ensuring robust polarity establishment.

Main Methods:

• Utilized the Caenorhabditis elegans zygote as a model organism.
• Investigated the function of PAR-3, PAR-6, CDC-42, and aPKC in cell polarization.
• Analyzed the formation and dynamics of distinct aPKC-containing protein assemblies.

Main Results:

• Identified two specialized aPKC-containing assemblies: a PAR-3-dependent assembly and a CDC-42-dependent assembly.
• The PAR-3 assembly promotes aPKC segregation but maintains it in an inactive state.
• The CDC-42 assembly leads to active but poorly segregated aPKC.

Conclusions:

• aPKC cycles between distinct functional assemblies to link cue-sensing and effector functions within the PAR network.
• This dynamic cycling is essential for the robust establishment of cell polarity.
• The interplay between PAR-3 and CDC-42 dependent assemblies provides a mechanism for precise spatial control of aPKC activity.