We are grateful to Daniela Rhodes, Yasunori Saheki, and David Drubin for critical reading of the manuscript. We thank Jackie Tan for helping with the TEM work. We thank Min Wu (NUS, Singapore) for sharing the Nikon imaging system for TIRF microscopy. We thank David Drubin for sharing the strains. We also thank the NTU Protein Production Platform (www.proteins.sg) for protein expression test and purification of Spa2-C. This study was supported by NTU start-up grant (M4081533), MOE Tier 2 (MOE2016-T2-1-005S), Tier 1 (RG38/17-S), SRIS (SIG18002/M4062479) to Y.M., and MOE Tier 2 (MOE2015-T2-1-078) to Y.-G.G. in Singapore.