Characterization of Neuronal Anillin and Borg Protein Localization and Function

Septins are filament-forming proteins that scaffold a host of proteins to their sites offunction. One such protein is anillin, that along with septins, mediates cytokinesis duringcell division. Research to date has focused on characterizing the role of anillin duringcytokinesis. Interestingly, anillin is most highly expressed in the central nervous system,which is in part composed of terminally differentiated, post-mitotic cells, such asneurons. Anillin has been characterized as a mitotic marker in neuronal cells, but perhapsits high expression in the poorly mitotic brain could indicate another, novel role ofanillin. Here we show that not only is anillin present in multiple primary central nervoussystem cells, it is also a smaller isoform of anillin, having an N-terminal truncation. Thetruncated anillin, localizes differently than the better characterized somatic cell anillin,being present in the cytoplasm and largely excluded from the nucleus. In addition, thiscytoplasmic truncated anillin localizes to the phagocytic cup, where it is involved inmediating phagocytosis. Interestingly, brain anillin still localizes to the cleavage furrowdespite its N-terminal truncation, and perhaps its function as an anchor for theactomyosin contractile ring to the cortex, is supplemented by other actin-binding proteincomplexes like the cadherin-catenin complex.The assembly of septin filaments is poorly understood. One of the best candidates forregulating septin filaments are the poorly understood Borg family of proteins that caninduce septin filament polymerization when overexpressed. Here we show that Borgproteins localize to multiple septin-containing structures and are involved in regulatingseptin polymerization into rings. Borg depletion studies also link them to multiple mitoticprocesses, which largely mirrors septin-depletion phenotypes. We also link Borgs toseptin recruitment at the primary cilia. In short, our results show that a novel form ofanillin exists in the brain, and is involved in phagocytosis. In addition, our Borg studiesfurther characterize their roles in septin-dependent phenotypes, as they are required fornormal mitosis progression, and septin recruitment to the ciliary axoneme.

Department dc:contributor.department

Biochemistry

Year dc:date.issued

2014

Author dc:creator

• Beise, Nolan

Advisor dc:contributor.advisor

• William, Trimble

• borgs
• central nervous system
• mitosis
• phagocytosis
• primary cilium
• septins

Handle dc:identifier.uri

http://hdl.handle.net/1807/68242

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/68242