April 29, 2013

There are many, many things in cell biology that can serve as models for fine art, but fewer are more stunning to me than a Purkinje neuron.  Purkinje neurons are some of the largest neurons in the brain, where they participate in motor control from the cerebellum.  Today’s image is from a paper describing what happens when a protein called rictor is depleted from Purkinje neurons.

The two multi-protein complexes mTORC1 and mTORC2 share sensitivity to inhibition by the immunosuppressive drug rapamycin, yet likely have distinct roles in cell function and development.  Each complex is composed of a distinct set of subunits—mTORC1 depends on the protein raptor, while mTORC2 depends on the protein rictor.  A recent paper describes an important role for mTORC2 in neuron size, morphology, and function.  Thomanetz and colleagues found that two different mouse lines lacking the mTORC2 protein rictor had smaller neurons with disrupted function, likely mediated through regulation of PKC (protein kinase C) isoforms.   mTORC1 activity was unaffected in these mutants.  When rictor was depleted from the entire central nervous system, motor function of the mice was affected.  When rictor was depleted from only Purkinje neurons, the cell type with the highest rictor expression, neurons were smaller and their morphology was abnormal.  In the images above, control Purkinje neurons (top) had only one primary dendrite compared with neurons lacking rictor (bottom), which had multiple primary dendrites (notated in different colors, right).  

Thomanetz, V., Angliker, N., Cloetta, D., Lustenberger, R., Schweighauser, M., Oliveri, F., Suzuki, N., & Ruegg, M. (2013). Ablation of the mTORC2 component rictor in brain or Purkinje cells affects size and neuron morphology originally published in the Journal of Cell Biology, 201 (2), 293-308 DOI: 10.1083/jcb.201205030