Scaffold proteins and immune-cell signalling

Scaffold proteins are known to have an important role in signal transduction but their mechanisms of activation are still unclear. In this Review, recent studies that have shed light on the function of cytoplasmic scaffold proteins in immune-cell signalling are discussed. Over the past 20 years great progress has been made in defining most of the key signalling pathways that functionally regulate immune cells. Recently, it has become clear that scaffold proteins have a crucial role in regulating many of these signalling cascades. By binding two or more components of a signalling pathway, scaffold proteins can help to localize signalling molecules to a specific part of the cell or to enhance the efficacy of a signalling pathway. Scaffold proteins can also affect the thresholds and the dynamics of signalling reactions by coordinating positive and negative feedback signals. In this Review, we focus on recent progress in the understanding of the function of scaffold proteins in immune cells.