Islet-Brain (IB)/JNK-Interacting Proteins (JIPs): Future Targets for the Treatment of Neurodegenerative Diseases?

Islet-Brain (IB) proteins [also called JNK-interacting proteins (JIPs)] are scaffold proteins that are mainly expressed in the pancreatic islets and in the brain. Functionally, the IB family is composed of IB1, IB2, IB3, and IB4 each with distinct splice variants. The IB family of proteins regulates several mitogen-activated protein kinase (MAPK) pathways by tethering their components and modifying the spectrum of substrates targeted by the MAPKs. The expression of these proteins is developmentally regulated, indicating that they play important functions during brain formation. While it is currently unclear what the precise physiological functions of the IB proteins are, there are indications that they participate in subcellular targeting of signalling proteins and modulate cell survival. Synthetic derivatives of these proteins can efficiently counteract apoptotic signalling in cells and tissues and represent therefore promising protective agents against traumatic insults, including stroke and hypoxia. This review will focus on the molecular functions of the IB proteins and their potential implications in the development of several human pathologies.