Janssen Research & Development 1 article published in JoVE Medicine Coculture Analysis of Extracellular Protein Interactions Affecting Insulin Secretion by Pancreatic Beta Cells Charles Zhang1, Arthur T. Suckow2, Steven D. Chessler1,3 1Pediatric Diabetes Research Center, University of California, San Diego, 2Janssen Research & Development, 3Department of Medicine, University of California, San Diego Transcellular protein interactions are important determinants of pancreatic beta-cell function. Detailed here is a method—adapted from a coculture model of synaptogenesis—for investigating how specific transmembrane proteins influence insulin secretion. Transfected HEK293 cells express proteins of interest; beta cells do not need to be transfected or otherwise directly perturbed.