TY - JOUR T1 - Distinct Roles of c-Jun N-Terminal Kinase Isoforms in Neurite Initiation and Elongation during Axonal Regeneration JF - The Journal of Neuroscience JO - J. Neurosci. SP - 7804 LP - 7816 DO - 10.1523/JNEUROSCI.0372-10.2010 VL - 30 IS - 23 AU - Monia Barnat AU - Hervé Enslen AU - Friedrich Propst AU - Roger J. Davis AU - Sylvia Soares AU - Fatiha Nothias Y1 - 2010/06/09 UR - http://www.jneurosci.org/content/30/23/7804.abstract N2 - c-Jun N-terminal kinases (JNKs) (comprising JNK1–3 isoforms) are members of the MAPK (mitogen-activated protein kinase) family, activated in response to various stimuli including growth factors and inflammatory cytokines. Their activation is facilitated by scaffold proteins, notably JNK-interacting protein-1 (JIP1). Originally considered to be mediators of neuronal degeneration in response to stress and injury, recent studies support a role of JNKs in early stages of neurite outgrowth, including adult axonal regeneration. However, the function of individual JNK isoforms, and their potential effector molecules, remained unknown. Here, we analyzed the role of JNK signaling during axonal regeneration from adult mouse dorsal root ganglion (DRG) neurons, combining pharmacological JNK inhibition and mice deficient for each JNK isoform and for JIP1. We demonstrate that neuritogenesis is delayed by lack of JNK2 and JNK3, but not JNK1. JNK signaling is further required for sustained neurite elongation, as pharmacological JNK inhibition resulted in massive neurite retraction. This function relies on JNK1 and JNK2. Neurite regeneration of jip1−/− DRG neurons is affected at both initiation and extension stages. Interestingly, activated JNKs (phospho-JNKs), as well as JIP1, are also present in the cytoplasm of sprouting or regenerating axons, suggesting a local action on cytoskeleton proteins. Indeed, we have shown that JNK1 and JNK2 regulate the phosphorylation state of microtubule-associated protein MAP1B, whose role in axonal regeneration was previously characterized. Moreover, lack of MAP1B prevents neurite retraction induced by JNK inhibition. Thus, signaling by individual JNKs is differentially implicated in the reorganization of the cytoskeleton, and neurite regeneration. ER -