JIPs are JNK interacting proteins and bind to JNK cascade kinases. JIP1 and JIP3 were known to be adaptors linking cargo to Kinesin-I, a major molecular motor for axonal transport. Recent research sheds further light on JIPs' complex roles in axonal transport, namely in activation of Kinesin-I and in cargo release. In Drosophila, APLIP1/JIP1 allows the Kinesin-I complex to enable cargo release through activation of JNK signaling.1 In mammalian cell culture, JIP1 is necessary and, together with UNC-76/FEZ1, sufficient for activating Kinesin-I.2 I discuss and compare the many roles played by JIP1 and JIP3 through interactions with several distinct players, in retrograde as well as anterograde transport.

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