Lactate promotes plasticity gene expression by potentiating NMDA signaling in neurons.

L-lactate is a product of aerobic glycolysis that can be used by neurons as an energy substrate. Here we report that in neurons L-lactate stimulates the expression of synaptic plasticity-related genes such as Arc, c-Fos, and Zif268 through a mechanism involving NMDA receptor activity and its downstream signaling cascade Erk1/2. L-lactate potentiates NMDA receptor-mediated currents and the ensuing increase in intracellular calcium.

Rnd1 regulates axon extension by enhancing the microtubule destabilizing activity of SCG10.

The GTPase Rnd1 affects actin dynamics antagonistically to Rho and has been implicated in the regulation of neurite outgrowth, dendrite development, and axon guidance. Here we show that Rnd1 interacts with the microtubule regulator SCG10. This interaction requires a central domain of SCG10 comprising about 40 amino acids located within the N-terminal-half of a putative alpha-helical domain and is independent of phosphorylation at the four identified phosphorylation sites that regulate SCG10 activity.

Stathmin-like 2, a developmentally-associated neuronal marker, is expressed and modulated during osteogenesis of human mesenchymal stem cells.

Stathmin-like 2 (STMN2) protein, a neuronal protein of the stathmin family, has been implicated in the microtubule regulatory network as a crucial element of cytoskeletal regulation. Herein, we describe that STMN2 expression increases at both mRNA and protein levels during osteogenesis of human mesenchymal stem cells derived from adipose tissue (hMADS cells) and bone marrow (hBMS cells), whereas it decreases to undetectable levels during adipogenesis. STMN2 protein is localized in both Golgi and cytosolic compartments.

Stathmin family protein SCG10 differentially regulates the plus and minus end dynamics of microtubules at steady state in vitro: implications for its role in neurite outgrowth.

SCG10 (superior cervical ganglia neural-specific 10 protein) is a neuron specific member of the stathmin family of microtubule regulatory proteins that like stathmin can bind to soluble tubulin and depolymerize microtubules. The direct actions of SCG10 on microtubules themselves and on their dynamics have not been investigated previously. Here, we analyzed the effects of SCG10 on the dynamic instability behavior of microtubules in vitro, both at steady state and early during microtubule polymerization.

The control of microtubule stability in vitro and in transfected cells by MAP1B and SCG10.

In neurons, the regulation of microtubules plays an important role for neurite outgrowth, axonal elongation, and growth cone steering. SCG10 family proteins are the only known neuronal proteins that have a strong destabilizing effect, are highly enriched in growth cones and are thought to play an important role during axonal elongation. MAP1B, a microtubule-stabilizing protein, is found in growth cones as well, therefore it was important to test their effect on microtubules in the presence of both proteins.

Taxol and tau overexpression induced calpain-dependent degradation of the microtubule-destabilizing protein SCG10.

Microtubule-stabilizing and -destabilizing proteins play a crucial role in regulating the dynamic instability of microtubules during neuronal development and synaptic transmission. The microtubule-destabilizing protein SCG10 is a neuron-specific protein implicated in neurite outgrowth. The SCG10 protein is significantly reduced in mature neurons, suggesting that its expression is developmentally regulated.

Improved sciatic nerve regeneration by local thyroid hormone treatment in adult rat is accompanied by increased expression of SCG10.

Thyroid hormone plays an important role in regulating the development and regeneration of the nervous system. Our previous work showed that local administration of triiodothyronine (T3) at the level of transected rat sciatic nerve increased the number and diameter of regenerated axons, but the mechanism underlying the improved regeneration is still unclear. Here, we have investigated the effect of T3 on the expression of SCG10, a regulator of microtubule dynamics in growth cones.

Differential regulation of the growth-associated proteins GAP-43 and superior cervical ganglion 10 in response to lesions of the cortex and substantia nigra in the adult rat.

Investigation of the elements underlying synapse replacement after brain injury is essential for predicting the neural compensation that can be achieved after various types of damage. The growth-associated proteins superior cervical ganglion-10 and growth-associated protein-43 have previously been linked with structural changes in the corticostriatal system in response to unilateral deafferentation. To examine the regulation of this response, unilateral cortical aspiration lesion was carried out in combination with ipsilateral 6-hydroxydopamine lesion of the substantia nigra, and the time course of the contralateral cortical molecular response was followed.

Superficial and deep changes of cellular mechanical properties following cytoskeleton disassembly.

The cytoskeleton, composed of actin filaments, intermediate filaments, and microtubules, is a highly dynamic supramolecular network actively involved in many essential biological mechanisms such as cellular structure, transport, movements, differentiation, and signaling. As a first step to characterize the biophysical changes associated with cytoskeleton functions, we have developed finite elements models of the organization of the cell that has allowed us to interpret atomic force microscopy (AFM) data at a higher resolution than that in previous work. Thus, by assuming that living cells behave mechanically as multilayered structures, we have been able to identify superficial and deep effects that could be related to actin and microtubule disassembly, respectively.

Role of Ser50 phosphorylation in SCG10 regulation of microtubule depolymerization.

Members of the stathmin-like protein family depolymerize microtubules (MTs), probably due to the ability of each stathmin monomer to bind two tubulin heterodimers in a complex (T(2)S complex). SCG10, a member of this family, is localized in the growth cone of neurons. It has four identified sites of serine phosphorylation (S50, S63, S73, and S97).

Upregulation of activating transcription factor 3 (ATF3) by intrinsic CNS neurons regenerating axons into peripheral nerve grafts.

The expression of the transcription factor ATF3 in the brain was examined by immunohistochemistry during axonal regeneration induced by the implantation of pieces of peripheral nerve into the thalamus of adult rats. After 3 days, ATF3 immunoreactivity was present in many cells within approximately 500 mum of the graft. In addition, ATF3-positive cell nuclei were found in the thalamic reticular nucleus (TRN) and medial geniculate nuclear complex (MGN), from which most regenerating axons originate.

Restricted innervation of uterus and placenta during pregnancy: evidence for a role of the repelling signal Semaphorin 3A.

Because data from the literature suggest a lack of innervation of the placenta, we have investigated placenta, umbilical cord, and uterus to identify the molecules that play a role in regulating innervation in these organs. Neuropilin-1 and Plexin-A1 are cell surface proteins that form a receptor complex for Semaphorin 3A (Sema 3A), a secreted molecule mediating repelling signals for axonal growth cones. We have analyzed the expression of Neuropilin-1, Plexin-A1, and Semaphorin 3A in the above-mentioned tissues on the hypothesis that these molecules could regulate innervation in these organs during gestation.

L1/Laminin modulation of growth cone response to EphB triggers growth pauses and regulates the microtubule destabilizing protein SCG10.

During development, EphB proteins serve as axon guidance molecules for retinal ganglion cell axon pathfinding toward the optic nerve head and in midbrain targets. To better understand the mechanisms by which EphB proteins influence retinal growth cone behavior, we investigated how axon responses to EphB were modulated by laminin and L1, two guidance molecules that retinal axons encounter during in vivo pathfinding. Unlike EphB stimulation in the presence of laminin, which triggers typical growth cone collapse, growth cones co-stimulated by L1 did not respond to EphB.

Role of the microtubule destabilizing proteins SCG10 and stathmin in neuronal growth.

The related proteins SCG10 and stathmin are highly expressed in the developing nervous system. Recently it was discovered that they are potent microtubule destabilizing factors. While stathmin is expressed in a variety of cell types and shows a cytosolic distribution, SCG10 is neuron-specific and membrane-associated.

Transcriptional upregulation of SCG10 and CAP-23 is correlated with regeneration of the axons of peripheral and central neurons in vivo.

We have compared SCG10 and CAP-23 expression with that of GAP-43 during axonal regeneration in the peripheral and central nervous systems (PNS, CNS) of adult rats. SCG10, CAP-23, and GAP-43 mRNAs were strongly upregulated by motor and dorsal root ganglion (DRG) neurons following sciatic nerve crush, but not after dorsal rhizotomy. When the sciatic nerve was cut and ligated to prevent reinnervation of targets, expression of all three mRNAs was prolonged.

c-Jun N-terminal kinase-3 (JNK3)/stress-activated protein kinase-beta (SAPKbeta) binds and phosphorylates the neuronal microtubule regulator SCG10.

The neuronal growth-associated protein SCG10 is enriched in the growth cones of neurons where it destabilizes microtubules and thus contributes to the dynamic assembly and disassembly of microtubules. Since its microtubule-destabilizing activity is regulated by phosphorylation, SCG10 may link extracellular signals to rearrangements of the neuronal cytoskeleton. To identify signal transduction pathways that may lead to SCG10 phosphorylation, we tested a series of serine-threonine-directed protein kinases that phosphorylate SCG10 in vitro.

Expression of SCG10 and stathmin proteins in the rat olfactory system during development and axonal regeneration.

The membrane-associated protein SCG10 is expressed specifically by neuronal cells. Recent experiments have suggested that it promotes neurite outgrowth by increasing microtubule dynamics in growth cones. SCG10 is related to the ubiquitous but neuron-enriched cytosolic protein stathmin.

Differences in phosphorylation of human and chicken stathmin by MAP kinase.

Stathmin/Op18 is a highly conserved 19 kDa cytosolic phosphoprotein. Human and chicken stathmin share 93% identity with only 11 amino acid substitutions. One of the substituted amino acids is serine 25, which is a glycine in chicken stathmin.

Preliminary crystallographic study of a complex formed between the alpha/beta-tubulin heterodimer and the neuronal growth-associated protein SCG10.

Crystals of a complex formed between the alpha/beta-tubulin heterodimer and SCG10, a neuron-specific growth-associated protein, have been obtained by the hanging drop method. They belong to the space group P2(1)2(1)2(1), with unit cell parameters a = 56 A, b = 353 A, c = 466 A and four molecular complexes in the asymmetric unit. A complete X-ray diffraction data set to 6.

Localization and targeting of SCG10 to the trans-Golgi apparatus and growth cone vesicles.

SCG10 is a membrane-associated, microtubule-destabilizing protein of neuronal growth cones. Using immunoelectron microscopy, we show that in the developing cortex of mice, SCG10 is specifically localized to the trans face Golgi complex and apparently associated with vesicular structures in putative growth cones. Consistent with this, subcellular fractionation of rat forebrain extracts demonstrates that the protein is enriched in the fractions containing the Golgi apparatus and growth cone particles.

Identification of in vitro phosphorylation sites in the growth cone protein SCG10. Effect Of phosphorylation site mutants on microtubule-destabilizing activity.

SCG10 is a neuron-specific, membrane-associated protein that is highly concentrated in growth cones of developing neurons. Previous studies have suggested that it is a regulator of microtubule dynamics and that it may influence microtubule polymerization in growth cones. Here, we demonstrate that in vivo, SCG10 exists in both phosphorylated and unphosphorylated forms.

Differential distribution of stathmin and SCG10 in developing neurons in culture.

The neuron-specific protein SCG10 and the ubiquitous protein stathmin are two members of a family of microtubule-destabilizing factors that may regulate microtubule dynamics in response to extracellular signals. To gain insight into the function of these proteins in the nervous system, we have compared their intracellular distribution in cortical neurons developing in culture. We have used double-immunofluorescence microscopy with specific antibodies for stathmin and SCG10 in combination with antibodies for axonal, microtubule, and synaptic marker proteins.