The hyaluronan receptor RHAMM in noradrenergic fibers contributes to axon growth capacity of locus coeruleus neurons in an intraocular transplant model

The importance of RHAMM in the normal brain and gliomas: physiological and pathological roles

Although the literature about the functions of hyaluronan and the CD44 receptor in the brain and brain tumours is extensive, the role of the receptor for hyaluronan-mediated motility (RHAMM) in neural stem cells and gliomas remain poorly explored. RHAMM is considered a multifunctional receptor which performs various biological functions in several normal tissues and plays a significant role in cancer development and progression. RHAMM was first identified for its ability to bind to hyaluronate, the extracellular matrix component associated with cell motility control. Nevertheless, additional functions of this protein imply the interaction with different partners or cell structures to regulate other biological processes, such as mitotic-spindle assembly, gene expression regulation, cell-cycle control and proliferation. In this review, we summarise the role of RHAMM in normal brain development and the adult brain, focusing on the neural stem and progenitor cells, and discuss the current knowledge on RHAMM involvement in glioblastoma progression, the most aggressive glioma of the central nervous system. Understanding the implications of RHAMM in the brain could be useful to design new therapeutic approaches to improve the prognosis and quality of life of glioblastoma patients.

The scrambled story between hyaluronan and glioblastoma

Advances in cancer biology are revealing the importance of the cancer cell microenvironment on tumorigenesis and cancer progression. Hyaluronan (HA), the main glycosaminoglycan in the extracellular matrix, has been associated with the progression of glioblastoma (GBM), the most frequent and lethal primary tumor in the central nervous system, for several decades. However, the mechanisms by which HA impacts GBM properties and processes have been difficult to elucidate. In this review, we provide a comprehensive assessment of the current knowledge on HA's effects on GBM biology, introducing its primary receptors CD44 and RHAMM and the plethora of relevant downstream signaling pathways that can scramble efforts to directly link HA activity to biological outcomes. We consider the complexities of studying an extracellular polymer and the different strategies used to try to capture its function, including 2D and 3D in vitro studies, patient samples, and in vivo models. Given that HA affects not only migration and invasion, but also cell proliferation, adherence, and chemoresistance, we highlight the potential role of HA as a therapeutic target. Finally, we review the different existing approaches to diminish its protumor effects, such as the use of 4-methylumbelliferone, HA oligomers, and hyaluronidases and encourage further research along these lines in order to improve the survival and quality of life of GBM patients.

Regulation of Trophic Factor Expression by Innervating Target Regions in Intraocular Double Transplants

Trophic factors have been found to play a significant role both in long-term survival processes and in more rapid and dynamic processes in the brain and spinal cord. However, little is known regarding the regulation of expression of growth factors, and how these proteins interact on a cell-to-cell basis. We have studied protein levels of one growth factor known to affect the noradrenergic innervation of the hippocampal formation, namely brain-derived neurotrophic factor (BDNF). The purpose of the present study was to determine if appropriate innervation or contact between the LC noradrenergic neurons and their target, the hippocampus, affects expression of this growth factor in either brain region. Fetal brain stem tissue, containing the LC, and hippocampal formation were dissected from embryonic day 17 rat fetuses and transplanted together or alone into the anterior chamber of the eye of adult Fisher 344 rats. The tissue was grown together for 6 weeks, after which the animals were sacrificed and ELISAs for BDNF were undertaken. Transplantation to the anterior chamber of the eye increased the expression of BDNF in the hippocampal but not the brain stem tissue, compared with levels observed in fetal and adult rats in vivo. In addition, double grafting with hippocampal tissue more than tripled BDNF levels in brain stem grafts and doubled BDNF levels in the hippocampal portion of double grafts compared with hippocampal single grafts. Triple grafts containing basal forebrain, hippocampus, and brain stem LC tissue increased brain stem and hippocampal BDNF levels even further. Colchicine treatment of LC-hippocampal double grafts gave rise to a significant decrease in hippocampal BDNF levels to levels seen in single hippocampal grafts, while only a partial reduction of BDNF levels was seen in the brain stem portion of the same double grafts treated with colchicine. The findings suggest that an appropriate hippocampal innervation or contact with its target tissues is essential for regulation of BDNF expression in the brain stem, and that retrograde transport of BDNF can occur between double grafted fetal tissues in oculo.

Hyaluronan synthesis by developing cortical neurons in vitro

Hyaluronan is a linear glycosaminoglycan that forms the backbone of perineuronal nets around neurons in the cerebral cortex. However, it remains controversial whether neurons are capable of independent hyaluronan synthesis. Herein, we examined the expression of hyaluronan and hyaluronan synthases (HASs) throughout cortical neuron development in vitro. Enriched cultures of cortical neurons were established from E16 rats. Neurons were collected at days in vitro (DIV) 0 (4 h), 1, 3, 7, 14, and 21 for qPCR or immunocytochemistry. In the relative absence of glia, neurons exhibited HAS1–3 mRNA at all time-points. By immunocytochemistry, puncta of HAS2–3 protein and hyaluronan were located on neuronal cell bodies, neurites, and lamellipodia/growth cones from as early as 4 h in culture. As neurons matured, hyaluronan was also detected on dendrites, filopodia, and axons, and around synapses. Percentages of hyaluronan-positive neurons increased with culture time to ~93% by DIV21, while only half of neurons at DIV21 expressed the perineuronal net marker Wisteria floribunda agglutinin. These data clearly demonstrate that neurons in vitro can independently synthesise hyaluronan throughout all maturational stages, and that hyaluronan production is not limited to neurons expressing perineuronal nets. The specific structural localisation of hyaluronan suggests potential roles in neuronal development and function.

Downstream effector molecules in successful peripheral nerve regeneration

The robust axon regeneration that occurs following peripheral nerve injury is driven by transcriptional activation of the regeneration program and by the expression of a wide range of downstream effector molecules from neuropeptides and neurotrophic factors to adhesion molecules and cytoskeletal adaptor proteins. These regeneration-associated effector molecules regulate the actin-tubulin machinery of growth-cones, integrate intracellular signalling and stimulatory and inhibitory signals from the local environment and translate them into axon elongation. In addition to the neuronally derived molecules, an important transcriptional component is found in locally activated Schwann cells and macrophages, which release a number of cytokines, growth factors and neurotrophins that support neuronal survival and axonal regeneration and that might provide directional guidance cues towards appropriate peripheral targets. This review aims to provide a comprehensive up-to-date account of the transcriptional regulation and functional role of these effector molecules and of the information that they can give us with regard to the organisation of the regeneration program.

Neuronal c-Jun is required for successful axonal regeneration, but the effects of phosphorylation of its N-terminus are moderate

Although neural c-Jun is essential for successful peripheral nerve regeneration, the cellular basis of this effect and the impact of c-Jun activation are incompletely understood. In the current study, we explored the effects of neuron-selective c-Jun deletion, substitution of serine 63 and 73 phosphoacceptor sites with non-phosphorylatable alanine, and deletion of Jun N-terminal kinases 1, 2 and 3 in mouse facial nerve regeneration. Removal of the floxed c-jun gene in facial motoneurons using cre recombinase under control of a neuron-specific synapsin promoter (junΔS) abolished basal and injury-induced neuronal c-Jun immunoreactivity, as well as most of the molecular responses following facial axotomy. Absence of neuronal Jun reduced the speed of axonal regeneration following crush, and prevented most cut axons from reconnecting to their target, significantly reducing functional recovery. Despite blocking cell death, this was associated with a large number of shrunken neurons. Finally, junΔS mutants also had diminished astrocyte and microglial activation and T-cell influx, suggesting that these non-neuronal responses depend on the release of Jun-dependent signals from neighboring injured motoneurons. The effects of substituting serine 63 and 73 phosphoacceptor sites (junAA), or of global deletion of individual kinases responsible for N-terminal c-Jun phosphorylation were mild. junAA mutants showed decrease in neuronal cell size, a moderate reduction in post-axotomy CD44 levels and slightly increased astrogliosis. Deletion of Jun N-terminal kinase (JNK)1 or JNK3 showed delayed functional recovery; deletion of JNK3 also interfered with T-cell influx, and reduced CD44 levels. Deletion of JNK2 had no effect. Thus, neuronal c-Jun is needed in regeneration, but JNK phosphorylation of the N-terminus mostly appears to not be required for its function.

Studies on the hippocampal formation: From basic development to clinical applications: Studies on schizophrenia

The hippocampal formation plays a critical role in cognitive function. The developmental events that shape the hippocampal formation are continuing to be elucidated and their implications for brain function are emerging as well as applying those advances to interventions that have important possibilities for the treatment of brain dysfunction. The story told in this chapter is about the use of the in oculo transplant method to illuminate intrinsic and extrinsic features that underlie the development of the dentate gyrus and adjacent hippocampus and the role of one molecule in the hippocampus and schizophrenia. Schizophrenia, originally conceptualized as a dysfunction in dopaminergic neurotransmission, is now known to involve multiple neuronal systems. Dysfunction of hippocampal neurons is emerging as one of its signature pathological features. Basic insights into the development and function of hippocampal interneurons form the basis of a new treatment initiative for this illness. Evidence for the role of the alpha 7-nicotinic acetylcholine receptor in the development and function of these neurons in rodents has led to human trials of nicotinic agonists for cognitive dysfunction in schizophrenia and the possibility of improving hippocampal development in children at risk for schizophrenia by perinatal supplementation with choline, which can act as an alpha 7-nicotinic acetylcholine receptor agonist.

Effects of short-term and chronic olanzapine treatment on immediate early gene protein and tyrosine hydroxylase immunoreactivity in the rat locus coeruleus and medial prefrontal cortex

Atypical antipsychotic drugs, such as olanzapine, have been reported to activate the locus coeruleus (LC) and lead to acute expression of the Fos-like immediate early gene (IEG) protein in the LC and medial prefrontal cortex (mPFC). Stimuli that activate the LC have been reported to increase expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis. However, the effects of chronic treatment with olanzapine on IEG expression and the dose-dependence of the effects of olanzapine on IEG and TH expression are not known. Thus, we examined Fos-like, c-Jun, activating transcription factor 2 (ATF-2), early growth response 1 (Egr-1), early growth response 2 (Egr-2), and TH immunoreactivity expression in the LC and mPFC in rats receiving 2, 4, 8, or 15 mg/kg/day olanzapine by s.c. osmotic minipump for 4 h, 1 week, 2 weeks, or 4 weeks. ATF-2 expression was up-regulated at all treatment durations, while Egr-1 and Egr-2 were down-regulated in both the LC and mPFC. Fos-like expression was up-regulated through 2 weeks, but not 4 weeks, in both the LC and mPFC. C-Jun expression was up-regulated for 4 weeks in the LC and for 2 weeks, but not 4 weeks, in the mPFC. At all doses, there were rapid and sustained increases in TH immunoreactivity in the LC, but only delayed increases in the mPFC. These data indicate that olanzapine has rapid effects on IEG in the LC and mPFC, many of which are sustained through four weeks of treatment. Further, these data indicate that the delayed increase in TH expression in the mPFC parallels, and may play an important role in, the increased efficacy of olanzapine that emerges over time in humans.

Chronic high-dose haloperidol has qualitatively similar effects to risperidone and clozapine on immediate-early gene and tyrosine hydroxylase expression in the rat locus coeruleus but not medial prefrontal cortex

Acute administration of clozapine has been reported to activate the locus coeruleus (LC) and beta-adrenoceptor-dependent Fos immunoreactivity in the medial prefrontal cortex (mPFC) in rodents. Haloperidol is reported to exhibit a similar acute effect on LC firing and beta-adrenoceptor dependent Fos immunoreactivity in the mPFC but only at high doses. We compared the effects of chronic 4-week treatment with risperidone (1mg/kg/day s.c.), clozapine (10mg/kg/day s.c.) or a high dose of haloperidol (4mg/kg/day s.c.) on immediate-early gene protein (c-Fos, Egr-1 and Egr-2) and tyrosine hydroxylase (TH) expression. In the mPFC, haloperidol decreased, whereas clozapine increased, c-Fos immunoreactivity. Only haloperidol increased Egr-1 immunoreactivity. There was no significant effect on Egr-2 immunoreactivity. In the LC, both Egr-1 and Egr-2 expression was down regulated by all three antipsychotics. Clozapine and risperidone increased TH immunoreactivity in both mPFC and LC. Haloperidol caused a smaller increase in TH expression in the LC, but did not alter expression in the mPFC. In conclusion, despite qualitatively similar effects in the LC, chronic treatment with haloperidol had different effects to clozapine and risperidone in the mPFC. This may relate to the reported advantage of clozapine and risperidone over haloperidol against prefrontal cortical-dependent cognitive and negative symptoms.

Short-Term Effects of Adolescent Methylphenidate Exposure on Brain Striatal Gene Expression and Sexual/Endocrine Parameters in Male Rats

Exposure to methylphenidate (MPH) during adolescence is the elective therapy for attention deficit/hyperactivity disorder (ADHD) children, but raises major concerns for public health, due to possibly persistent neurobehavioral changes. Rats (30- to 44-days old) were administered MPH (2 mg/kg, i.p once daily) or saline (SAL). At the end of the treatment we collected plasma, testicular, liver, and brain (striatum) samples. The testes and liver were used to evaluate conventional reproductive and metabolic endpoints. Testes of MPH-exposed rats weighed more and contained an increased quantity of sperm, whereas testicular levels of testosterone (TST) were markedly decreased. The MPH treatment exerted an inductive effect on enzymatic activity of TST hydroxylases, resulting in increased hepatic TST catabolism. These findings suggest that subchronic MPH exposure in adolescent rats could have a trophic action on testis growth and a negative impact on TST metabolism. We have analyzed striatal gene expression profiles as a consequence of MPH exposure during adolescence, using microarray technology. More than 700 genes were upregulated in the striatum of MPH-treated rats (foldchange >1.5). A first group of genes were apparently involved in migration of immature neural/glial cells and/or growth of novel axons. These genes include matrix proteases (ADAM-1, MMP14), their inhibitors (TIMP-2, TIMP-3), the hyaluronan-mediated motility receptor (RHAMM), and growth factors (transforming growth factor-beta3 [TGF-beta3] and fibroblast growth factor 14 [FGF14]). A second group of genes were suggestive of active axonal myelination. These genes mediate survival of immature cells after contact with newly produced axonal matrix (laminin B1, collagens, integrin alpha 6) and stabilization of myelinating glia-axon contacts (RAB13, contactins 3 and 4). A third group indicated the appearance and/or upregulation of mature processes. The latter included genes for: K+ channels (TASK-1, TASK-5), intercellular junctions (connexin30), neurotransmitter receptors (adrenergic alpha 1B, kainate 2, serotonin 7, GABA-A), as well as major proteins responsible for their transport and/or anchoring (Homer 1, MAGUK MPP3, Shank2). All these genes were possibly involved in synaptic plasticity, namely the formation, maturation, and stabilization of new neural connections within the striatum. MPH treatment seems to potentiate synaptic plasticity, which is an age-dependent developmental phenomenon that adolescent rats are very likely to show, compared to adults. Our observations suggest that adolescent MPH exposure causes only transient changes in reproductive and hormonal parameters, and a more enduring enhancement of neurobehavioral plasticity.

Heterogeneous targeting of centrifugal inputs to the glomerular layer of the main olfactory bulb

The centrifugal systems innervating the olfactory bulb are important elements in the functional regulation of the olfactory pathway. In this study, the selective innervation of specific glomeruli by serotonergic, noradrenergic and cholinergic centrifugal axons was analyzed. Thus, the morphology, distribution and density of positive axons were studied in the glomerular layer of the main olfactory bulb of the rat, using serotonin-, serotonin transporter- and dopamine-beta-hydroxylase-immunohistochemistry and acetylcholinesterase histochemistry in serial sections. Serotonin-, serotonin transporter-immunostaining and acetylcholinesterase-staining revealed a higher heterogeneity in the glomerular layer of the main olfactory bulb than previously reported. In this sense, four types of glomeruli could be identified according to their serotonergic innervation. The main distinctive feature of these four types of glomeruli was their serotonergic fibre density, although they also differed in their size, morphology and relative position throughout the rostro-caudal main olfactory bulb. In this sense, some specific regions of the glomerular layer were occupied by glomeruli with a particular morphology and a characteristic serotonergic innervation pattern that was consistent from animal to animal. Regarding the cholinergic system, we offer a new subclassification of glomeruli based on the distribution of cholinergic fibres in the glomerular structure. Finally, the serotonergic and cholinergic innervation patterns were compared in the glomerular layer. Sexual differences concerning the density of serotonergic fibres were observed in the atypical glomeruli (characterized by their strong cholinergic innervation). The present report provides new data on the heterogeneity of the centrifugal innervation of the glomerular layer that constitutes the morphological substrate supporting the existence of differential modulatory levels among the entire glomerular population.

Linkage of schizophrenia with chromosome 1q loci in Taiwanese families

A positive linkage of schizophrenia with chromosome 1q loci has been reported in Caucasian patients. This study was designed to evaluate the linkage of schizophrenia with markers of the 1q22-44 region in 52 Taiwanese families with at least two affected siblings. In the region 1q22-31 (17.8 cM), marker D1S1679 had a maximal proportion (0.57, P=0.03) of shared identity by descent (IBD) under a narrow phenotype (DSM-IV schizophrenia only). In the region 1q42-44 (26.8 cM), the marker D1S251, located near the breakpoint of a balanced translocation t (1;11) (q42.1;q14.3) segregated with schizophrenia, and also near the neurodevelopment-related 'Disrupted in Schizophrenia 1' gene, had a maximum NPL score of 1.73 (P=0.03) under the narrow phenotype model and 2.18 (P=0.01) under the broad phenotype model comprised of schizophrenia, schizoaffective disorder, and other nonaffective psychotic disorders as defined by DSM-IV criteria. The marker D1S2836 also had a maximal proportion (0.57, P=0.05) of shared IBD under the broad model. These findings may provide guidance for positional cloning studies on candidate genes in the 1q22-31 and 1q41-44 regions.

Glycosaminoglycan levels and proteoglycan expression are altered in the hippocampus of patients with mesial temporal lobe epilepsy

Extracellular matrix proteoglycans (PGs) and glycosaminoglycans (GAGs) play a crucial role in cell differentiation and synaptogenesis by modulating neurite outgrowth. The chondroitin sulfate (CS)-rich PG, the receptor protein tyrosine phosphatase zeta/beta (RPTP zeta/beta), has been related to neural morphogenesis and axon guidance. Hippocampal sclerosis is the most frequent pathologic finding in patients with intractable mesial temporal lobe epilepsy (MTLE), which is associated with neuron loss, reactive gliosis, and mossy fiber sprouting. In the present study, we investigated the concentration of CS, heparan sulfate (HS) and hyaluronic acid (HA) in the hippocampus and temporal neocortex as well as RPTP zeta/beta expression in the hippocampus of patients with MTLE. Compared to autopsy control tissue, epileptic hippocampi showed a significantly increased concentration of CS (224%; p=0.0109) and HA (146%; p=0.039). HS was instead similar to control values. No differences were found in the concentration of CS, HS, or HA in the temporal neocortex of epileptic patients when compared to control values. In contrast, RPTP zeta/beta immunoreactivity was induced in astrocytes of the inner molecular layer of the dentate gyrus of the sclerotic hippocampus. Because matrix compounds have been associated with tissue injury and repair, the present findings suggest that changes in PGs and GAGs might be related to damage-induced gliosis and neuronal reorganization in the hippocampus of MTLE patients.

Extracellular matrix components are altered in the hippocampus, cortex, and cerebrospinal fluid of patients with mesial temporal lobe epilepsy

PURPOSE

This work studied the profile of glycosaminoglycans (GAGs) in the hippocampus, cortex, and cerebrospinal fluid of patients with temporal lobe epilepsy (TLE).

METHODS

The GAGs were analyzed by agarose gel electrophoresis, enzymatic degradation, and enzyme-linked immunosorbent assay (ELISA).

RESULTS

The hippocampus of TLE patients showed increased levels of chondroitin sulfate and hyaluronic acid against normal levels of these GAGs in the neocortex and cerebrospinal fluid (CSF).

CONCLUSIONS

These results suggest that these matrix components could be involved in the pathophysiology of TLE.

Identification of sequence, protein isoforms, and distribution of the hyaluronan-binding protein RHAMM in adult and developing rat brain

The protein RHAMM (for "receptor for hyaluronan-mediated motility"; CD168) is a member of the hyaladherin family of hyaluronan-binding proteins. RHAMM has a role in cell signaling, migration, and adhesion via interactions with hyaluronan, microtubules, actin, calmodulin, and components of the extracellular regulated kinase (erk) signaling pathway. Based on previous findings of potentially similar roles in neural cells in culture, we investigated the molecular characteristics, protein expression profile, and distribution of RHAMM in rat brain. Reverse transcriptase-polymerase chain reaction (RT-PCR) using RNA isolated from adult rat brain yielded a single RHAMM sequence of 2.1 kilobases encoding a protein of 82.4 kDa. RHAMM is subject to alternate splicing in other systems, but no RT-PCR evidence was found for splice variants in brain, although our analysis does not rule out this possibility. The amino acid sequence displayed homology with human and murine RHAMM (74% and 80%, respectively) but contained only one copy of a 21-amino-acid sequence that is repeated five times in the murine homologue. By using anti-RHAMM antibodies, several RHAMM isoforms were identified in brain. Immunohistochemically, RHAMM was found in the vast majority of neurons and in many oligodendrocytes throughout brain, with heterogeneous levels among cell populations, and was confined to the somata and initial processes of these cells. RHAMM was detected in neurons of cerebral cortex and most subcortical and brainstem structures at postnatal day 1 and exhibited an adult distribution pattern by postnatal day 5. High levels were detected in oligodendrocytes by postnatal day 10. The widespread expression of RHAMM in adult and developing brain implies a role for this protein and its ligand hyaluronan in key events of cell signaling and cytoskeletal regulation in the CNS.

Differential involvement of the hyaluronan (HA) receptors CD44 and receptor for HA-mediated motility in endothelial cell function and angiogenesis

Hyaluronan (HA), an important glycosaminoglycan constituent of the extracellular matrix, has been implicated in angiogenesis. It appears to exert its biological effects through binding interactions with at least two cell surface receptors: CD44 and receptor for HA-mediated motility (RHAMM). Recent in vitro studies have suggested potential roles for these two molecules in various aspects of endothelial function. However, the relative contribution of each receptor to endothelial functions critical to angiogenesis and their roles in vivo have not been established. We therefore investigated the endothelial expression of these proteins and determined the effects of antibodies against RHAMM and CD44 on endothelial cell (EC) function and in vivo angiogenesis. Both receptors were detected on vascular endothelium in situ, and on the surface of cultured EC. Further studies with active blocking antibodies revealed that anti-CD44 but not anti-RHAMM antibody inhibited EC adhesion to HA and EC proliferation, whereas anti-RHAMM but not CD44 antibody blocked EC migration through the basement membrane substrate, Matrigel. Although antibodies against both receptor inhibited in vitro endothelial tube formation, only the anti-RHAMM antibody blocked basic fibroblast growth factor-induced neovascularization in mice. These data suggest that RHAMM and CD44, through interactions with their ligands, are both important to processes required for the formation of new blood vessels.

Subcellular distribution, calmodulin interaction, and mitochondrial association of the hyaluronan-binding protein RHAMM in rat brain

The CNS contains high levels of the glycosaminoglycan hyaluronan, and neural cells express a variety of proteins that are members of the hyaladherin family of hyaluronan-binding proteins. We have previously shown that the hyaladherin RHAMM (receptor for hyaluronan-mediated motility; CD168) is expressed by neural cells in culture; plays a role in astrocyte motility, neurite migration, and axonal growth; and is widely distributed in neurons and oligodendrocytes of developing and adult rat CNS. Here we demonstrate differential localization of various forms of RHAMM in subcellular fractions of adult rat brain. Western blotting indicated the presence of 66, 75, and 85-90 kDa molecular weight RHAMM forms in whole-brain homogenates. Subfractionation revealed enrichment of the 66 and 85-90 kDa forms in soluble fractions, whereas the 75 kDa form was enriched in mitochondrial fractions. This latter form was retained in osmotically shocked mitochondria, but was liberated by alkali carbonate, suggesting a nonintrinsic mitochondrial membrane association. By double immunohistochemical labeling for RHAMM and the mitochondrial marker cytochrome oxidase, RHAMM was localized to isolated mitochondria in vitro and to neuronal mitochondria in vivo. Hyaluronan-sepharose chromatography and cetylpiridinium chloride precipitation confirmed the hyaluronan-binding capacity of RHAMM forms. By calmodulin-affinity chromatography, endogenously expressed brain RHAMM was demonstrated to bind calmodulin in a Ca2+-dependent manner. These results, together with reports of RHAMM association with actin and microtubules in other systems, suggest a role of RHAMM in calmodulin-mediated cell signaling to cytoskeletal elements and/or mitochondria in the CNS and invoke novel functions of its interactions with hyaluronan.

Sequence, protein expression and extracellular-regulated kinase association of the hyaladherin RHAMM (receptor for hyaluronan mediated motility) in PC12 cells

Differentiation of PC12 cells by nerve growth factor (NGF) or fibroblast growth factor-2 (FGF2) is dependent on signaling mediated by extracellular regulated kinase (ERK). We investigated the involvement of receptor for hyaluronan mediated motility (RHAMM) in this signaling pathway. A single RHAMM 3.2 kb transcript was detected in PC12 RNA. Reverse transcriptase-polymerase chain reaction generated a 2141 bp cDNA that had identical sequence to rat brain RHAMM and showed no evidence of alternate splicing. Several RHAMM species were identified by Western blotting. Immunohistochemistry showed RHAMM localization to the cytoskeleton, neurites and growth cones. Following stimulation of PC12 cells with NGF or FGF2 RHAMM was co-immunoprecipitated by phosphorylation-specific anti-ERK antibodies, indicating a role for RHAMM in ERK signaling in PC12 cells.

Control of enzymatic degradation of hyaluronan by divalent cations

Enzymatic degradation of hyaluronan (HA) by testicular hyaluronidase (HAase, hyaluronate 4-glucanohydrolase) requires inclusion of mono- or divalent cations in the reaction mixture. Most divalent cations activated HAase with equal potency; however, Cu2+ suppressed degradation, and Ca2+ showed a concentration-dependent regulation of size of the oligosaccharide products. Careful selection of HAase assay parameters is critical for discovery of novel HAase inhibitors and for preparation of controlled-size oligosaccharide fragments.