Triggered immobilization of proteins in the plasma membrane of living cells into functional micropatterns is established by using an adaptor protein, which is comprised of an antiGFP nanobody fused to the HaloTag protein. Efficient in situ reorganization of the type I interferon receptor subunits as well as intact, fully functional signaling complexes in living cells are achieved by this method.

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Type 2 diabetes (T2D) is diagnosed based on high fasting plasma glucose (FPG) or high glucose at the two-hour time point of an oral glucose tolerance test (OGTT). However, clinical data show that this may not be appropriate for all ethnic groups. For example, Koreans often have high glucose one hour into the OGTT but normal FPG and two-hour glucose. We have developed a comprehensive model of the pathogenesis of T2D, based on the model of Topp et al (J. Theor Biol. 2000), modified to include a subsystem for exocytosis, and have applied it to simulate OGTTs. The model suggests that the Korean OGTT pattern results a defect in early (first-phase) insulin secretion and a delay in late (second phase) secretion. This may contribute to the high prevalence of T2D in Korea and points to the danger of under-diagnosis using the standard criteria. In contrast, African Americans typically exhibit strong first-phase insulin secretion relative to Whites and second phase insulin secretion similar to that of Whites. This group therefore also has normal FPG and two-hour glucose during OGTT, which again can result in under-diagnosis of their high risk for T2D. The simulations for this case suggest that the strong first phase results from a large readily releasable pool of insulin granules but that the diabetes risk results from trafficking of reserve vesicles to the plasma membrane that is more susceptible to deterioration under the stress of insulin resistance. We conclude that a detailed analysis of insulin secretion dynamics is necessary to properly interpret OGTT results for ethnically diverse populations. 513-Pos Board B293Quantitative Imaging of the Exocytosis Machinery Assembly The assembly of the secretory machinery is a poorly understood prerequisite for regulated exocytosis. Current models propose that the arriving vesicle docks at the plasma membrane by binding to either raft-like clusters (nanodomains) of SNARE proteins or to structural proteins such as RIM1, in both cases implying at least partial assembly of the secretory machinery prior to docking. In contrast, we recently showed that docking coincides with and requires recruitment of syntaxin and munc18 into nanodomains at the docking site, suggesting assembly after docking. Here we extend on this work and present live cell imaging-based quantification for many exocytosis proteins (including syntaxin, SNAP25, Munc18, Munc13, Rab3þ27, Rabphilin, Granuphilin, RIM1, CaV1.2, EPAC, NSF, alfaSNAP; all tagged with EGFP) at the insulin granule release site during docking, priming and exocytosis. We find that the Rab3 interacting protein RIM1 was the only protein enriched at docking sites prior to vesicle tethering and docking. Further recruitment of RIM1 to the docking site occurred during granule maturation into the releasable pool (priming), suggesting roles in both docking and priming. None of the other proteins were present before granule arrival, but these were instead recruited during docking or even later during priming. Granules that successfully docked carried Rab3...

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