Anaplastic lymphoma kinase (ALK) is a receptor-type protein tyrosine kinase that is expressed preferentially in neurons of the central and peripheral nervous systems at late embryonic stages. To elucidate the role of ALK in neurons, we developed an agonist monoclonal antibody (mAb) against the extracellular domain of ALK. Here we show that mAb16-39 elicits tyrosine phosphorylation of endogenously expressed ALK in human neuroblastoma (SK-N-SH) cells. Stimulation of these cells with mAb16-39 markedly induces the tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1), Shc, and c-Cbl and also their interaction with ALK and activation of ERK1/2. Furthermore, we show that continuous incubation with mAb16-39 induces the cell growth and neurite outgrowth of SK-N-SH cells. These responses are completely blocked by MEK inhibitor PD98059 but not by the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin, indicating an essential role of the mitogen-activated protein kinase (MAP kinase) signaling cascade in ALK-mediated growth and differentiation of neurons.

We have attempted to characterize the rat leukocyte integrin, CD11/CD18, by the use of newly generated monoclonal antibodies (mAb) WT.1 (anti-CD11a) and WT.3 (anti-CD18) in conjunction with an mAb, OX42, reactive with a rat integrin-like molecule, with respect to the biochemistry, cellular distribution and function. The conclusion that the mAb WT.1 and WT.3 specifically recognize the rat CD11a and CD18, respectively, was based on: (a) their ability to inhibit homotypic aggregation of splenic concanavalin A (Con A) blasts; (b) sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the antigens recognized; (c) their ability to inhibit binding of Con A blasts to the purified ligand, namely the ICAM-1 antigen and (d) their blocking abilities in mixed leukocyte reaction. In the rat, CD18 has an apparent molecular mass of 95-100 kDa and can associate with at least three distinct alpha subunits of 160-170 kDa (CD11a), 140-150 kDa and 120-130 kDa. The latter two are precipitated by OX42 from M phi but not from unstimulated lymphocytes. They presumably represent the rat CD11b and CD11c, respectively. Rat thymocytes, PBL, thoracic duct lymphocytes, monocytes and neutrophils expressed differential levels of CD11a and CD18. Peritoneal M phi showed virtually no CD11a expression, although CD18 was expressed at levels similar to those seen on blood monocytes, showing an interesting pattern of LFA-1 expression regulation in this cell lineage. Both WT.1 (anti-CD11a) and WT.3 (anti-CD18) apparently recognize a "low-affinity" as well as a "high-affinity" form of LFA-1 and do not discriminate between the two.

We investigated the localization of major gangliosides in adult rat brain by an immunofluorescence technique with mouse monoclonal antibodies (MAbs). Five MAbs (GMB16, GMR17, GGR12, GMR5 and GMR13) that specifically recognize gangliosides GM1, GD1a, GD1b, GT1b and GQ1b, respectively, were used. We have found that there is a cell type-specific expression of the ganglioside in the rat central nervous system. In cerebellar cortex, GM1 was expressed in myelin and some glial cells. GD1a was detected exclusively in the molecular layer. GD1b and GQ1b were present restrictedly on the granular layer; GD1b was detected on the surface of the granular cell bodies, whereas GQ1b was present in the cerebellar glomerulus. GT1b was distributed intensely in both the molecular layer and the granular layer. In cerebral cortex, GM1 was detected in some glial cells. Dense staining was limited to the white matter. GD1a was distributed in layers I, II/III and Va, and the upper part of layer VI, whereas GQ1b was localized in layers IV and Vb, and the lower part of layer VI. GD1b was detected beneath layer III. GT1b appeared to be distributed throughout all layers. In other regions, such as hippocampal formation and spinal cord, the expression of the ganglioside was also highly localized to a specific cell type and layer.

We compared two recombinant a-galactosidases developed for enzyme replacement therapy for Fabry disease, agalsidase alfa and agalsidase beta, as to specific a-galactosidase activity, stability in plasma, mannose 6-phosphate (M6P) residue content, and effects on cultured human Fabry fibroblasts and Fabry mice. The specific enzyme activities of agalsidase alfa and agalsidase beta were 1.70 and 3.24 mmol h À1 mg protein À1 , respectively, and there was no difference in stability in plasma between them. The M6P content of agalsidase beta (3.6 mol/mol protein) was higher than that of agalsidase alfa (1.3 mol/mol protein). The administration of both enzymes resulted in marked increases in a-galactosidase activity in cultured human Fabry fibroblasts, and Fabry mouse kidneys, heart, spleen and liver. However, the increase in enzyme activity in cultured fibroblasts, kidneys, heart and spleen was higher when agalsidase beta was used. An immunocytochemical analysis revealed that the incorporated recombinant enzyme degraded the globotriaosyl ceramide accumulated in cultured Fabry fibroblasts in a dose-dependent manner, with the effect being maintained for at least 7 days. Repeated administration of agalsidase beta apparently decreased the number of accumulated lamellar inclusion bodies in renal tubular cells of Fabry mice.

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The phosphoinositide 3-kinase (PI3K) pathway has been extensively studied in neuronal function and morphogenesis. However, the precise molecular mechanisms of PI3K activation and its downstream signalling in neurons remain elusive. Here, we report the identification of the Neuronal tYrosine-phosphorylated Adaptor for the PI 3-kinase (NYAP) family of phosphoproteins, which is composed of NYAP1, NYAP2, and Myosin16/NYAP3. The NYAPs are expressed predominantly in developing neurons. Upon stimulation with Contactin5, the NYAPs are tyrosine phosphorylated by Fyn. Phosphorylated NYAPs interact with PI3K p85 and activate PI3K, Akt, and Rac1. Moreover, the NYAPs interact with the WAVE1 complex which mediates remodelling of the actin cytoskeleton after activation by PI3K-produced PIP 3 and Rac1. By simultaneously interacting with PI3K and the WAVE1 complex, the NYAPs bridge a PI3K-WAVE1 association. Disruption of the NYAP genes in mice affects brain size and neurite elongation. In conclusion, the NYAPs activate PI3K and concomitantly recruit the downstream effector WAVE complex to the close vicinity of PI3K and regulate neuronal morphogenesis.

A mammalian-like sugar moiety was created in glycoprotein by Saccharomyces cerevisiae in combination with bacterial alpha-mannosidase to produce a more economic enzyme replacement therapy for patients with Fabry disease. We introduced the human alpha-galactosidase A (alpha-GalA) gene into an S. cerevisiae mutant that was deficient in the outer chains of N-linked mannan. The recombinant alpha-GalA contained both neutral (Man(8)GlcNAc(2)) and acidic ([Man-P](1-2)Man(8)GlcNAc(2)) sugar chains. Because an efficient incorporation of alpha-GalA into lysosomes of human cells requires mannose-6-phosphate (Man-6-P) residues that should be recognized by the specific receptor, we trimmed down the sugar chains of the alpha-GalA by a newly isolated bacterial alpha-mannosidase. Treatment of the alpha-GalA with the alpha-mannosidase resulted in the exposure of a Man-6-P residue on a nonreduced end of oligosaccharide chains after the removal of phosphodiester-linked nonreduced-end mannose. The treated alpha-GalA was efficiently incorporated into fibroblasts derived from patients with Fabry disease. The uptake was three to four times higher than that of the nontreated alpha-GalA and was inhibited by the addition of 5 mM Man-6-P. Incorporated alpha-GalA was targeted to the lysosome, and hydrolyzed ceramide trihexoside accumulated in the Fabry fibroblasts after 5 days. This method provides an effective and economic therapy for many lysosomal disorders, including Fabry disease.

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