TOAD-64, a gene expressed early in neuronal differentiation in the rat, is related to unc-33, a C. elegans gene involved in axon outgrowth

Abstract

Using two-dimensional gel electrophoresis we previously identified membrane-associated proteins that are upregulated over the course of neurogenesis. One of these, TOAD-64 (Turned On After Division, 64 kDa), is expressed immediately after neuronal birth and is dramatically downregulated in the adult. The gene encoding TOAD-64 has now been cloned, and its sequence shows homology to the unc-33 gene from C. elegans, mutations in which lead to aberrations in axon outgrowth. Northern and in situ hybridization show that TOAD-64 mRNA is enriched in the nervous system and is developmentally regulated in parallel with the protein. The expression of the TOAD-64 protein and gene coincident with initial neuronal differentiation and the downregulation when the majority of axon growth is complete suggests a role in axon elaboration. Three additional lines of evidence support this possibility: TOAD-64 is upregulated following neuronal induction of P19 and PC12 cells; the protein is found in lamellipodia and filopodia of growth cones; and axotomy of the sciatic nerve induces reexpression. While the sequence of TOAD-64 lacks a signal sequence and therefore is likely to encode a cytoplasmic protein, biochemical experiments demonstrate that the protein is tightly, but noncovalently, associated with membranes. The data presented here suggest that TOAD-64 could be a central element in the machinery underlying axonal outgrowth and pathfinding, perhaps playing a role in the signal transduction processes that permit growing axons to choose correct routes and targets.

Generation of Functional Inhibitory Neurons in the Adult Rat Hippocampus

“…The majority of GAD 65 ϩ -BrdU ϩ cells had the morphological characteristics (irregular/triangular cells bodies) of GABAergic interneurons located in the subgranule zone. Subsequently, we stained these sections with TUC-4, which labels immature neurons (Minturn et al, 1995). We found that the GAD 65 ϩ -BrdU ϩ cells were colabeled by TUC-4 (GAD 65 ϩ -BrdU ϩ -TUC-4 ϩ ) (Fig.…”

Cdk5‐mediated phosphorylation of CRMP‐2 enhances its interaction with CaV2.2

“…Whole-cell calcium currents were isolated using the following solutions: external (bath) medium (in mM): NaCl 128, KCl 5, MgCl 2 1, BaCl 2 10, D-glucose 10, HEPES-Na 10, and tetraethylammonium-Cl 10; with an osmolarity of 300 mosm/l and pH 7.3; patch electrode intracellular solution: CsCl 2 110, EGTA 10, MgSO 4 1, HEPES(Cs) 25, ATP 2, and GTP 0.2; osmolarity 305 mosm/l, pH 7.4. Tetrodotoxin (1 lM; Alomone Laboratories) was added in the bath solution to block Na + and Ltype Ca 2+ channels.…”

“…Initially identified in chick sensory neurons as a protein responsible for growth cone retraction in response to negative guidance signals in the semaphorin 3A (Sema3A) pathway [1], CRMP-2 analogues were subsequently identified in Caenorhabditis elegans (uncoordinated protein-33 (Unc-33)) [2], in rodents ((named turned on after development 64 (TOAD-64)) in rats and Unc-33 like phosphoprotein (Ulip) in mice) [3][4][5], in humans (HUlip) [6,7] and in Drosophila Melanogaster [8]. Together with its established roles in neurite growth and retraction and kinesin-dependent axonal transport, mapping the CRMP-2 interactome has revealed previously unappreciated functions including affecting microtubule dynamics, protein endocytosis and vesicle recycling, as well as synaptic assembly (see reviews by Hensley [9] and Strittmatter [10]).…”

TUC-4b, a Novel TUC Family Variant, Regulates Neurite Outgrowth and Associates with Vesicles in the Growth Cone

“…Two additional members of this family, TUC-1 and TUC-3, were identified by homology to TUC-2 and TUC-4 (Wang and Strittmatter, 1996). Indirect evidence for a role of the TUCs in axon outgrowth comes from the observation that TUC-4 is expressed in growth cones and is upregulated in motor neurons during axonal regeneration after sciatic nerve lesion (Minturn et al, 1995a). A role for TUC-2 in axon guidance is suggested by the observation that antibodies to CRMP-62 (TUC-2) can inhibit semaphorin-3A-mediated growth cone collapse (Goshima et al, 1995).…”