Thy-1 multimerization is correlated with neurite outgrowth.
Thy-1 is abundantly expressed in the vertebrate nervous system. Perturbation studies in vitro suggest that Thy-1 inhibits neurite outgrowth and stabilizes neuronal processes (N. K. Mahanthappa and P. H. Patterson. (1992). Thy-1 involvement in neurite outgrowth: Perturbation by antibodies, phospholipase C, and mutation. Dev. Biol. 150,47-59). We here report that Thy-1 participates in several types of homophilic interactions, each with differential sensitivity to reduction and boiling. The relative abundance of the multimeric forms of Thy-1 vary with the cell's ability to sprout neurites. Gel filtration chromatography of sympathetic neuron and PC12 cell lysates reveals that Thy-1 immunoreactivity appears in 25-, 45-, and 150-kDa forms. In neurons, Thy-1 immunoreactivity is distributed equally in all three forms, whereas in PC12 cells, the majority of Thy-1 immunoreactivity is found in the higher molecular weight forms. When PC12 cells are induced to sprout neurites with NGF, the Thy-1 size distribution becomes identical to that of neurons. The three forms of Thy-1 immunoreactivity are likely to be homomultimers of Thy-1 because immunoaffinity-purified, soluble Thy-1 also forms complexes similar in size to those found in neuronal extracts. To test whether Thy-1 multimerization may occur through interactions like those between immunoglobulin heavy and light chains, synthetic peptides corresponding to candidate sites for such associations in Thy-1 were tested for their effects on multimerization and neurite outgrowth. One peptide increases the amount of monomeric Thy-1 relative to total Thy-1, and promotes outgrowth. These results suggest that multimeric forms of Thy-1 inhibit process outgrowth and neurite sprouting by stabilizing the surface membrane and/or underlying cytoskeleton.
Division of Biology, California Institute of Technology, Pasadena 91125.
N K
NK
Mahanthappa
P H
PH
Patterson
D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000032:analysis* / Q000737:chemistry; D002462:Cell Membrane / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects; D005728:Ganglia, Sympathetic / Q000166:cytology; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000737:chemistry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016501:Neurites / Q000187:drug effects* / Q000648:ultrastructure; D010449:Peptide Mapping; D010455:Peptides / Q000494:pharmacology; D011108:Polymers; D051381:Rats; D018800:Thy-1 Antigens
D000954:Antigens, Surface; D008562:Membrane Glycoproteins; D010455:Peptides; D011108:Polymers; D018800:Thy-1 Antigens