ABSTRACT
Intracellular trafficking is a field that has been intensively studied for years and yet there remains much to be learned. Part ofthe reason that there is so much obscurity remaining in this field is due to all the pathways and the stages that define cellulartrafficking. One of the major steps in cellular trafficking is fusion. Fusion is defined as the terminal step that occurs when acargo-laden vesicle arrives at the proper destination. There are two types of fusion within a cell: homotypic and heterotypicfusion. Homotypic fusion occurs when the two membranes merging together are of the same type such as vacuole tovacuole fusion. Heterotypic fusion occurs when the two membranes at play are of different types such as when anendosomal membrane fuses with a Golgi membrane. In this review, we will focus on all the protein components – Rabs,Golgins, Multisubunit tethers, GTPases, protein phosphatases and SNAREs – that have been known to function in both ofthese types of fusion. We hope to develop a model of how all of these constituents function together to achieve membranefusion. Membrane fusion is a biological process absolutely necessary for proper intracellular trafficking. Due to the degreeof importance multiple proteins are required for it to be properly carried through. Whether we are talking about heterotypicor homotypic fusion, any defects in the fusion machinery can result in disease states such as Parkinson’s and Alzheimer’sdisease. Although much research has significantly expanded our knowledge of fusion, there is still much more to belearned.