Rapid axonal transport of the neural cell adhesion molecule

Abstract

The neural cell adhesion molecule (NCAM) is a cell-surface glycoprotein that mediates cell-cell interactions in the nervous system during development. In the present study, we demonstrate that NCAM is axonally transported in 3-d-old chick retinal ganglion cells and that it travels within the fast component of axonal transport (FC). Proteins were radiolabeled in retinal ganglion cell bodies after intraocular injection of %-methionine. The presence of radiolabeled NCAM in the optic nerves and contralateral tecta was detected by specific immunoadsorption to a monoclonal antibody. Major radioactive polypeptide bands at relative mobilities of approximately 200,000, 150,000, and 120,000 Mr (after SDS-PAGE) were recognized by the anti-NCAM antibody. These bands comigrated in l-dimensional gels with components of purified NCAM from chick brain. The 2 largest NCAM polypeptides (at 200,000 and 150,000 Mr) were found to be transported in this system, while the 120,000 Mr form was apparently not transported. The ratio and electrophoretie profiles of the 2 transported forms of NCAM remained similar in the retina, optic nerve, chiasm, tract, and tectum, suggesting that there is no interconversion of the 2 major polypeptides. The fraction of NCAM in the %-labeled FC proteins appears to be at least an order of magnitude less than in the plasma membrane, suggesting that the turnover rate of NCAM at this age is slower than for other membrane proteins of the CNS.The neural cell adhesion molecule (NCAM), a cell-surface glycoprotein, mediates cell-cell adhesion during development of nerve tissue (for review, see Rutishauser, 1983). NCAM plays an important role during neurite fasciculation (Rutishauser et al., 1978a), in axon-muscle interaction , and in the association of nerve growth cones with glial precursors (Silver and Rutishauser, 1984).In the present study, we have examined the axonal transport characteristics of the neural cell adhesion molecule. Since there is no protein synthetic machinery within the axon, the molecule must be supplied to the neurite and its terminal by transport within 1 of the 3 major axonal transport rate-components. Each of the 3 major rate-components is thought to convey a cytoplasmic structure within the axon: the fast component (FC) (moving at approximately 250 mm/d) provides membranes and membrane proteins, while the 2 slow components (moving at 0.2 and 2 mm/d) convey cytoplasmic matrix and cytoskeleton, respectively (Lasek, 1980;Lasek et al., 1984).Received Dec. 30, 1985; revised May 8, 1986; accepted May 30, 1986. We wish to thank R. J. , 1983; Gennarini et al., 1984a, b) with a largely uniform distribution on the growth cone, axon shaft, and cell soma (Rutishauser et al., 1978b). It was therefore predicted that NCAM would be transported within the FC of axonal transport.Although the FC of axonal transport has been the subject of study for a number of years, only a few rapidly transported proteins have been well characterized: notably the Na+-K+ ATPase (Baittinger and Willard, 1981;Specht and...

Localization of mRNA for neural cell adhesion molecule (N-CAM) polypeptides in neural and nonneural tissues by in situ hybridization.

“…In contrast, in situ hybridization analysis for myelin basic protein (19) and microtubule-associated protein 2 mRNAs (20) has shown that the mRNAs encoding these proteins actually are transported to their final destination in processes before translation. Our observations that the N-CAM mRNA was localized in cell bodies, whereas protein was also found at high levels in fibers, suggest that the compartmentalization of the N-CAM protein occurs posttranslationally at the level of protein transport, confirming previous studies of the axonal transport of N-CAM (28). The observations of polarity modulation of N-CAM (5, 18) and of interaction of N-CAM with cytoskeletal molecules (16,17) are also consistent with the idea that the protein is synthesized in the cell body and then transported.…”

Kinesin-1 promotes post-Golgi trafficking of NCAM140 and NCAM180 to the cell surface

“…This observation is not surprising, given that NCAMΔCT could be considered to be a functional and structural equivalent of the NCAM120 isoform of NCAM, which is anchored to the membrane through GPI and lacks an intracellular domain and, hence, is transported by mechanisms distinct from those of NCAM180 and NCAM140 (Garner et al, 1986;Nybroe et al, 1986). Our observation that cell surface levels of NCAMΔCT are similar to or even higher than those for NCAM180 indicates that KLC1 is not required for cell surface delivery of NCAM, but rather suggests that this interaction plays a role in regulation of NCAM transport.…”

“…In axons, NCAM is distributed by fast axonal transport (Garner et al, 1986;Nybroe et al, 1986). In dendrites and glial cell processes, NCAM also needs to be distributed to the cell surface after its transport to the sites of insertion.…”

Expression and function of neural cell adhesion molecule during limb regeneration.

“…8 and 9). As in the case of neurotrophic factor(s), NCAM has been reported to be axonally transported in the fast component (10). It has been proposed that NCAM can serve as an adhesive substrate for guidance of axon growth cones through a terrain containing cells that also express this molecule.…”