The NCAM-derived P2 peptide facilitates recovery of cognitive and motor function and ameliorates neuropathology following traumatic brain injury.

The neural cell adhesion molecule (NCAM) plays a crucial role during development and regeneration of the nervous system, mediating neuronal differentiation, survival and plasticity. Moreover, NCAM regulates learning and memory. A peptide termed P2, corresponding to a 12-amino-acid sequence in the second immunoglobulin (Ig)-like module of NCAM, represents the natural cis-binding site for the first NCAM Ig module. The P2 peptide targets NCAM, thereby inducing a number of intracellular signaling events leading to the stimulation of neurite outgrowth and promotion of neuronal survival in vitro. The present study evaluated the effect of the P2 peptide on functional and histological outcomes following traumatic brain injury inflicted by a cortical cryogenic lesion. Lesioned rats were injected subcutaneously with P2 peptide, 5 mg/kg daily for 15 days beginning 2 h after injury. This treatment significantly improved postlesion recovery of motor and cognitive function, reduced neuronal degeneration, protected cells against oxidative stress, and increased reactive astrogliosis and neuronal plasticity in the sublesional area. P2 appeared rapidly in blood and cerebrospinal fluid after subcutaneous administration and remained detectable in blood for up to 5 h. The results suggest that P2 has therapeutic potential for the treatment of traumatic brain injury.

Effects of P2, a peptide derived from a homophilic binding site in the neural cell adhesion molecule on learning and memory in rats.

The neural cell adhesion molecule (NCAM) plays a pivotal role in neural development, regeneration, synaptic plasticity, and memory processes. P2 is a 12-amino-acid peptide derived from the second immunoglobulin-like (Ig) module of NCAM mediating cis-homophilic interactions between NCAM molecules present on the same cell. P2 is a potent NCAM agonist, capable of promoting neuronal differentiation and survival in vitro. The aim of this study was to assess the effect of P2 on learning and memory. Rats treated with P2 intracerebroventricularly (1 h prior to test) performed significantly better than controls in the reinforced T-maze, a test of spatial working memory. Further, rats treated with P2 exhibited decreased anxiety-like behavior while learning the T-maze task. In the social recognition test, both intracerebroventricular (1 h prior to test) and systemic (1 and 24 h prior to test) P2 treatment enhanced short-term social memory and counteracted (administration 24 h prior test) scopolamine-induced social memory impairment. In contrast, P2 (1 h prior to test) did not significantly improve long-term (24 h) retention of social memory, nor did it have any significant effects on long-term memory evaluated by the Morris water maze (administration between 2 days before training and 5.5 h posttraining). In the open field test, P2 (1 h prior to test) decreased general locomotion and rearing, but did not influence any other anxiety-related behaviors, indicating only a minimal influence on baseline anxiety levels. Taken together, these data indicate that in vivo P2 enhances short-term memory and protects against the amnestic effects of scopolamine, while modulating emotional behavior in a learning or novelty-related task.

A neural cell adhesion molecule-derived peptide reduces neuropathological signs and cognitive impairment induced by Abeta25-35.

By means of i.c.v. administration of preaggregated oligomeric beta-amyloid (Abeta)25-35 peptide it was possible in rats to generate neuropathological signs related to those of early stages of Alzheimer's disease (AD). Abeta25-35-administration induced the deposition of endogenously produced amyloid protein. Furthermore, quantitative immunohistochemistry demonstrated time-related statistically significant increases in amyloid immunoreactivity, tau phosphorylation, microglial activation, and astrocytosis, and stereological investigations demonstrated statistically significant increased neuronal cell death and brain atrophy in response to Abeta25-35. Finally, the Abeta25-35-administration led to a reduced short-term memory as determined by the social recognition test. A synthetic peptide termed FGL derived from the neural cell adhesion molecule (NCAM) was able to prevent or, if already manifest, strongly reduce all investigated signs of Abeta25-35-induced neuropathology and cognitive impairment. The FGL peptide was recently demonstrated to be able to cross the blood-brain-barrier. Accordingly, we found that the beneficial effects of FGL were achieved not only by intracisternal, but also by intranasal and s.c. administration of the peptide. Furthermore, FGL-treatment was shown to inhibit the activity of GSK3beta, a kinase implicated in signaling regulating cell survival, tau phosphorylation and the processing of the amyloid precursor protein (APP). Thus, the peptide induced a statistically significant increase in the fraction of GSK3beta phosphorylated on the Ser9-position, a posttranslational modification known to inhibit the activity of the kinase. Hence, the mode of action of FGL with respect to the preventive and curative effects on Abeta25-35-induced neuropathological manifestations and cognitive impairment involves the modulation of intracellular signal-transduction mediated through GSK3beta.

A neural cell adhesion molecule-derived fibroblast growth factor receptor agonist, the FGL-peptide, promotes early postnatal sensorimotor development and enhances social memory retention.

The neural cell adhesion molecule (NCAM) belongs to the immunoglobulin (Ig) superfamily and is composed extracellularly of five Ig-like and two fibronectin type III (F3) modules. It plays a pivotal role in neuronal development and synaptic plasticity. NCAM signals via a direct interaction with the fibroblast growth factor receptor (FGFR). A 15-amino-acid long peptide, the FG loop (FGL) peptide, that is derived from the second F3 module of NCAM has been found to activate FGFR1. We here report that the FGL peptide, when administered intranasally to newborn rats, accelerated early postnatal development of coordination skills. In adult animals s.c. administration of FGL resulted in a prolonged retention of social memory. We found that FGL rapidly penetrated into the blood and cerebrospinal fluid after both intranasal and s.c. administration and remained detectable in the fluids for up to 5 hours.

Not growth associated protein GAP-43 (B-50), but its fragment GAP-43-3 (B-60) predominates in rat brain during development.

The participation of the nerve termini growth associated protein GAP-43 in neurite outgrowth and targeting is well documented. Commonly, besides GAP-43 itself, two big fragments devoid of four (GAP-43-2, IB-50) and of about 40 (GAP-43-3, B-60) N-terminal residues were co-isolated from brain. In adult brain, GAP-43 significantly prevails over the fragments. To find their relative amounts during development, rat brain proteins were isolated on different stages of embryonal and post-natal development and subjected to gel electrophoresis in 0.9 M acetic acid-2.5 M urea system. The bands of GAP-43 protein family were detected on Western blots. We show that in developing brain (until 5th post-natal day), a proteolysis of GAP-43 near Ser(41) that results in GAP-43-3 accumulation is activated. We hypothesize that just the functions that can be performed by the GAP-43 fragments are of importance for developing brain.

Enhanced level of site-specific proteolysis of GAP-43 protein during early stages of brain development.

GAP-43 protein of nerve terminals (B-50, F1, F57, pp46, neuromodulin) is thought to be one of key proteins involved in the control of outgrowth of neurites, release of neuromediators, synapse plasticity, etc. GAP-43 is usually considered as a whole protein. Along with the intact protein, nerve cells also contain two large native fragments of GAP-43 deprived of four or of about forty N-terminal amino acid residues (GAP-43-2 and GAP-43-3, respectively). The full-length GAP-43 is predominant in the mature brain. However, the ratio of the full-length protein and its fragments can vary under different physiological conditions. Changes in the GAP-43 proteins (the full-length protein and its fragments) were studied during embryonal and postnatal development of rat brain. The GAP-43 proteins were found to be expressed not later than on the 12-13th day of embryogenesis. Then their contents increased, and, until the 10th day after birth, GAP-43-3 dominated rather than the full-length protein. It is suggested that during this period the activity of a specific protease, which cleaves the N-terminal peptide of about 40 residues from the full-length GAP-43 molecule, is increased. The cleavage occurs in the region responsible for the interaction of GAP-43 with calmodulin. In the full-length molecule, this region is responsible also for the recognition of Ser41 residue by protein kinase C during phosphorylation. Another functionally important region that determines, in particular, the attachment of GAP-43 to the plasma membrane is cleaved from the main part of the molecule together with the N-terminal peptide. Thus, the specific fragmentation of GAP-43 that depends on developmental stage should be considered as a controlled structural rearrangement fundamentally affecting the functions of this protein.