Transmembrane cytoskeletal modulation in preterminal growing axons: I. Arrest of bulk and organelle transport in goldfish retinal ganglion cell axons regenerating in vitro by lectins binding to sialoglycoconjugates

Goldfish retinal ganglion cell (RGC) axons regenerating in vitro exhibit a novel mode of axoplasmic transport that entails a rapid bidirectional bulk redistribution of axoplasm, "packaged" as protruding varicosities and non-protruding phase-dense inclusions (Koenig et al.: J. Neurosci. 5:715-729, 1985; Edmonds and Koenig Brain Res. 406:288-293, 1987). We have used phase-contrast video microscopy to study transmembrane effects of surface-binding lectins on bulk transport and transport of single visible organelles in RGC axons. Our findings show that certain lectins which crosslink sialoglycoconjugates, such as wheat germ agglutinin (WGA) and the more specific sialic acid-binding lectin Limax flavus agglutinin (LFA), induce a rapid inhibition of transport activity. The LFA-induced inhibition of transport can be reversed by appropriate simple sugar haptens, and can also be antagonized by pretreatment with cytochalasin D. One of the consequences of LFA binding is an increase in RITC-conjugated phalloidin fluorescence staining of preterminal axons. The latter observation in conjunction with the antagonistic action of cytochalasin D suggests that one possible explanation for the transmembrane arrest of transport induced by crosslinking of surface sialoglycoconjugates may involve a polymerization and/or reorganization of the actin filament network which hinders translocation of mobile axoplasmic components.