ABSTRACT
The neuronal adhesion glycoprotein F3 is a multifunctional molecule of the immunoglobulin superfamily that displays heterophilic binding activities. In the present study, NrCAM was identified as the functional receptor mediating the inhibitory effect of F3 on axonal elongation from cerebellar granule cells. F3Fc-conjugated microspheres binding to neuronal growth cones resulted from heterophilic interaction with NrCAM but not with L1. Time-lapse video-microscopy indicated that F3Fc beads bind at the leading edge and move retrogradely to reach the base of the growth cone within a lapse of 30-60 seconds. Such velocity (5.7 microm/minute) is consistent with a coupling between F3 receptors and the retrograde flow of actin filaments. When actin filaments were disrupted by cytochalasin B, the F3Fc beads remained immobile at the leading edge. The retrograde mobility appeared to be dependent on NrCAM clustering since it was induced upon binding with cross-linked but not dimeric F3Fc chimera. These data indicate that F3 may control growth cone motility by modulating the linkage of its receptor, NrCAM, to the cytoskeleton. They provide further insights into the mechanisms by which GPI-anchored adhesion molecules may exert an inhibitory effect on axonal elongation.
Subject(s)
Actins/metabolism , Cell Adhesion Molecules, Neuronal/metabolism , Cell Adhesion Molecules , Cerebellum/metabolism , Growth Cones/metabolism , Animals , Axons/metabolism , Cell Adhesion Molecules, Neuronal/genetics , Cells, Cultured , Cerebellum/cytology , Chick Embryo , Contactins , Humans , Leukocyte L1 Antigen Complex , Ligands , Male , Membrane Glycoproteins/genetics , Membrane Glycoproteins/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Video , Microspheres , Neural Cell Adhesion Molecules/genetics , Neural Cell Adhesion Molecules/metabolism , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolismABSTRACT
The neural cell adhesion molecule L1 can be induced by antibodies in indirect immunofluorescence procedures to co-redistribute on the surface membrane of cultured mouse neuroblastoma cells with the 180 kDa component of N-CAM, but not with the 140 kDa component of N-CAM, the H-2 histocompatibility antigen or antigens recognized by polyspecific antibodies to mouse liver membranes. These observations indicate a differential and close molecular association between L1 and the N-CAM component with the larger intracellular domain.
Subject(s)
Antigens, Surface/metabolism , Cell Membrane/metabolism , Neuroblastoma/metabolism , Animals , Antigens/immunology , Antigens, Surface/immunology , Cell Adhesion Molecules , Cells, Cultured , Clone Cells , Fluorescent Antibody Technique , Mice , Neuroblastoma/immunology , Neuroblastoma/pathology , Tissue DistributionABSTRACT
The rodent neural cell adhesion molecule (N-CAM) consists of three glycoprotein chains of 180, 140, and 120 kD in their adult forms. Although the proportions of the three components are known to change during development and differ between brain regions, their individual distribution and function are unknown. Here we report studies carried out with a monoclonal antibody that specifically recognizes the 180-kD component of mouse N-CAM (N-CAM180) in its highly sialylated embryonic and less glycosylated adult forms. In primary cerebellar cell cultures, N-CAM180 antibody reacts intracellularly with all types of neural cells including astrocytes, oligodendrocytes, and neurons. During cerebellar, telencephalic, and retinal development N-CAM180 is detectable by indirect immunohistology in differentiated neural cells, but, in contrast to total N-CAM, not in their proliferating precursors in the ventricular zone and primordial and early postnatal external granular layer. In monolayer cultures of C1300 neuroblastoma cells, N-CAM180 appears by immunofluorescence more concentrated at contact points between adjacent cells, while N-CAM comprising the 180- and 140-kD component shows a more uniform distribution at the plasma membrane. Treatment of neuroblastoma cells with dimethylsulfoxide, which promotes differentiation, induces a shift toward the predominant expression of N-CAM180. These observations support the notion that N-CAM180 is expressed selectively in more differentiated neural cells and suggest a differential role of N-CAM180 in the stabilization of cell contacts.
Subject(s)
Antigens, Surface/biosynthesis , Cerebellum/growth & development , Aging , Animals , Animals, Newborn , Antibodies, Monoclonal , Antigens, Surface/isolation & purification , Cell Adhesion Molecules , Cell Membrane/metabolism , Cells, Cultured , Cerebellum/cytology , Cerebellum/metabolism , Fluorescent Antibody Technique , Macromolecular Substances , Mice , Mice, Inbred C57BL , Molecular WeightABSTRACT
The gross morphology of the neck muscles of a cricket (Gryllus campestris) and their innervation are described and compared with a locust (Schistocerca gregaria). The motor neurons innervating the neck muscles were stained in crickets and locusts with cobalt chloride introduced via the nerve endings in the muscle. The two species show overall similarities, not only in position of the neck motor neurons in suboesophageal, prothoracic, and mesothoracic ganglia but also in motor neuron morphology. However, muscle 60 in the cricket is innervated by a unique motor neuron with its axon in prothoracic nerve 3, instead of sharing motor neurons in suboesophageal nerve 8 and mesothoracic nerve 1 with muscle 59, as in locust. Muscle 62 has the same attachments and innervation with similar motor neurons in cricket and locust but a different mechanical function in the two species. The findings are discussed with respect to possible segmental homologies and to the origins of the muscles as either dorso-ventral or longitudinal. As several muscles share the same motor neurons, we suggest that neck muscle function be described in terms of "behavioural units of action."
