Neogenin regulates neuronal survival through DAP kinase

Abstract

The repulsive guidance molecule (RGM) is a membrane-bound protein that has diverse functions in the developing central nervous system. Identification of neogenin as a receptor for RGM provided evidence of its cell death-inducing activity in the absence of RGM. Here, we show that the serine/threonine kinase death-associated protein kinase (DAPK) is involved in the signal transduction of neogenin. Neogenin interacts with DAPK and reduces DAPK autophosphorylation on Ser308 in vitro. Neogenininduced cell death is abolished in the presence of RGM or by blocking DAPK. Although neogenin overexpression or RGM downregulation in the chick neural tube in vivo induces apoptosis, coexpression of the dominant-negative mutant or smallinterference RNA of DAPK attenuates this proapoptotic activity. Thus, RGM/neogenin regulates cell fate by controlling the DAPK activity. Cell Death and Differentiation (2008) 15, 1593-1608 doi:10.1038/cdd.2008; published online 27 June 2008The repulsive guidance molecule (RGM) is a glycosylphosphatidylinositol -anchored glycoprotein that does not share significant homology with any other proteins. RGM was originally identified as a membrane-bound protein having repulsive and growth cone collapse-inducing activities in the chick retinotectal system. 1 This molecule was later purified and cloned from the posterior part of the chick tectum. 2 RGM contains a putative autoproteolytic or an unstable cleavage site, and the cleaved mature protein has a molecular mass of 33 kDa. 3,4 Recently, neogenin was identified as an RGM receptor; 5 this protein was originally isolated from embryonic chicken cerebellum as a deleted in colorectal cancer (DCC) homologue. 6 During central nervous system (CNS) development, neogenin mediates axon guidance by binding either RGM or netrin-1 7 and controls neuronal differentiation and survival. 8,9 In the ligand-free state, neogenin induces apoptosis; 10 therefore, it belongs to the structurally unrelated, functionally defined family of 'dependence receptors'. This indicates that the absence of a ligand induces self-activation of the receptor with its subsequent proteolytic processing, thereby triggering apoptotic cell death. 11,12 Neogenin overexpression or RGMa downregulation at E1.5 in the area of the developing chick neural tube resulted in an increase in the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells. 10 However, the signal transduction mechanism that induces cell death is completely unknown and remains to be analyzed.When attempting to elucidate the function of RGM and neogenin, we identified the serine/threonine kinase deathassociated protein kinase (DAPK) to be an interactor of neogenin. DAPK is a crucial intracellular protein that mediates cell death by its serine threonine kinase activity. 13-16 DAPK has a multidomain structure that comprises a kinase domain, a calmodulin (CaM)-binding motif, eight ankyrin repeats, a cytoskeleton-binding region, and a death domain; the kinase and death domains are both impo...

Targeting Repulsive Guidance Molecule A to Promote Regeneration and Neuroprotection in Multiple Sclerosis

“…The RGMa receptor neogenin plays an important role in cell death regulation in the embryonic and adult CNS (Fujita et al, 2008) mediated by two proteins directly bound to neogenin and released upon RGMa binding: death-associated protein kinase (DAPK) and LIM domain only 4 (LMO4) (Schaffar et al, 2008;Goldschneider et al, 2008;Fujita et al, 2008). These two proteins influence different intracellular pathways: DAPK, on the one hand, affects cellular survival by activating the apoptotic pathway, and LMO4, on the other hand, affects the cytoskeleton and gene expression.…”

Neogenin, a Receptor for Bone Morphogenetic Proteins

“…For G, n ϭ 5. *, p Ͻ 0.01; **, p Ͻ 0.05. sis in some but not all of the cell types (17,18). To test the validity of this possibility, we performed the MTT assay to assess the cell viability.…”

Dependence receptors: a new paradigm in cell signaling and cancer therapy

“…Moreover, phosphorylation of the myosin light chain by DAPK leads to membrane blebbing, a hallmark of programmed cell death (Gozuacik and Kimchi, 2006). Interestingly, it was recently suggested that UNC5H2 was not the only DR to trigger apoptosis through DAPK, as neogenin was also shown to interact with DAPK and to require DAPK for apoptosis induction (Fujita et al, 2008), in the same way that DCC, UNC5H1, 2 and 3 also require lipid raft association to induce cell death . Caspase 3 activation Apoptosis Figure 5 Model of cell death induction by UNC5H2/UNC5B.…”