| First Author | Ramalingam L | Year | 2014 |
| Journal | Biochem J | Volume | 464 |
| Issue | 2 | Pages | 251-8 |
| PubMed ID | 25190515 | Mgi Jnum | J:217823 |
| Mgi Id | MGI:5615864 | Doi | 10.1042/BJ20140845 |
| Citation | Ramalingam L, et al. (2014) Doc2b serves as a scaffolding platform for concurrent binding of multiple Munc18 isoforms in pancreatic islet beta-cells. Biochem J 464(2):251-8 |
| abstractText | Biphasic glucose-stimulated insulin secretion (GSIS) from pancreatic beta-cells involves soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor (SNARE) protein-regulated exocytosis. SNARE complex assembly further requires the regulatory proteins Munc18c, Munc18-1 and Doc2b. Munc18-1 and Munc18c are required for first- and second-phase GSIS respectively. These distinct Munc18-1 and Munc18c roles are related to their transient high-affinity binding with their cognate target (t-)SNAREs, Syntaxin 1A and Syntaxin 4 respectively. Doc2b is essential for both phases of GSIS, yet the molecular basis for this remains unresolved. Because Doc2b binds to Munc18-1 and Munc18c via its distinct C2A and C2B domains respectively, we hypothesized that Doc2b may provide a plasma membrane-localized scaffold/platform for transient docking of these Munc18 isoforms during GSIS. Towards this, macromolecular complexes composed of Munc18c, Doc2b and Munc18-1 were detected in beta-cells. In vitro interaction assays indicated that Doc2b is required to bridge the interaction between Munc18c and Munc18-1 in the macromolecular complex; Munc18c and Munc18-1 failed to associate in the absence of Doc2b. Competition-based GST-Doc2b interaction assays revealed that Doc2b could simultaneously bind both Munc18-1 and Munc18c. Hence these data support a working model wherein Doc2b functions as a docking platform/scaffold for transient interactions with the multiple Munc18 isoforms operative in insulin release, promoting SNARE assembly. |
