Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

52-POS Board 26 The Function of Dynamin 2 in Podosome-Regulated Postsynaptic Neuromuscular Junction Maturation Shan-Shan Lin , Ya-Wen Liu. National Taiwan University Institute of Molecular Medicine, Taipei City, Taiwan. Podosomes are dynamic, actin-rich structures and best-characterized for cell-matrix interactions, migration, and matrix degradation in monocytic lineage and cancer cells. Recently it has been reported that podosomes are also present in aneurally formed postsynaptic neuromuscular junction (NMJ), and a GTPase, dynamin-2, is enriched at the postsynaptic podosome. Dynamin- 2 is a mechanochemical enzyme, best-known for mediating endocytosis at presynaptic neuron membrane. Therefore, the presence of dynamin-2 in postsynaptic NMJ is novel and remains to be investigated. To understand the function of dynamin-2 at postsynaptic NMJ, we utilized cultured C2C12 myotubes and found that dynamin-2 is enriched at the peripheral of the podosomes and tightly surrounds the actin core. Podosomes with more dynamin-2 surrounding are taller than those without or with partial dynamin-2 ring. Interestingly, treatment with GTPase inhibitor, dynasore, can further increase the height of podosomes in myotubes. Through in vitro actin bundling assay, we demonstrated that dynamin-2 has promising actin bundling activity, and dynamin-2 mutations with altered assembly ability have abnormal actin bundling efficiency. Finally, we found that expression of the hyper-assembly dynamin-2, but not the wild type or membrane fission defective mutations, result in disturbance to the cytoskeleton of postsynaptic NMJ in Drosophila. Taken together, our finding suggests that dynamin-2 plays a structural role in podosome maturation through actin bundling activity, and therefore affect the cytoskeleton organization in podosome-regulated postsynaptic NMJ maturation.

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