You’ve probably seen animations of microtubule transport (MT) where a kinesin motor protein strolls along a microtubule, towing a massive cargo vesicle tethered above like a Macy’s Thanksgiving parade balloon. The N-terminal motor head domain with its shuffling “feet” has been finely dissected by researchers, but the interaction of the C-terminal tail with its cargo is still one of those areas where all the players, let alone the entire mechanism, is not completely understood.
Now looking more closely at microtubule transport in a rat hippocampal neuron, Xiaobo Bai and ASCB members Eva Karasmanis and Elias Spiliotis at Drexel University in Philadelphia have spotted an old player in a novel role at the C-terminal of kinesin KIF17. They found septin 9, a member of the GTP-binding family of proteins known for shaping the spatial organization of membrane and cytoskeletal proteins, acting as a delivery regulator of microtubule transport in neurons by interacting with kinesin KIF17. In the March 15 issue of MBoC, the researchers show that septin 9 interferes with KIF17 binding to its cargo, slowing the transport of NMDA (N-methyl-D-asparate) receptors in neurons, probably by blocking another adaptor protein. NMDA receptors are major players in the formation of dendritic networks between neurons, affecting synaptic plasticity and thus learning. But why septin 9 is involved in all this is still to be discovered, say the researchers.
