Anillin Phosphorylation Controls Timely Membrane Association and Successful Cytokinesis.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Cytokinesis requires a contractile ring of actin and myosin to divide cells.
• Anillin is a scaffold protein essential for linking the contractile ring to the cell membrane and RhoA.
• The precise molecular mechanisms regulating anillin's timely function during cytokinesis are not fully understood.

Purpose of the Study:

• To investigate the role of anillin phosphorylation in its recruitment to the equatorial membrane during cytokinesis.
• To identify specific phosphorylation sites on anillin critical for cytokinesis.
• To elucidate the molecular basis for anillin's function in cell division.

Main Methods:

• Surveyed 46 phosphorylated residues on human anillin to determine their role in cytokinesis.
• Utilized site-directed mutagenesis to create non-phosphorylatable (S635A) and phosphomimetic (S635D) anillin mutants.
• Employed time-lapse videomicroscopy to observe anillin localization and cytokinesis progression.
• Developed and used a phosphospecific antibody to detect anillin phosphorylation at S635.

Main Results:

• Phosphorylation regulates the efficient recruitment of human anillin to the equatorial membrane.
• Serine 635 (S635) was identified as a key site mediating cytokinesis.
• Mutation of S635 to alanine (S635A) disrupted anillin localization and caused cytokinesis failure.
• A phosphomimetic mutation (S635D) partially restored anillin localization.
• Phosphorylation at S635 was detected in late cytokinesis, but not early, potentially due to adjacent phosphorylation.

Conclusions:

• Anillin recruitment to the equatorial cortex at anaphase onset is enhanced by phosphorylation.
• Phosphorylation at S635 is critical for successful cytokinesis.
• These findings reveal a novel regulatory mechanism for anillin function during cell division.