Journal of Neuroscience, Vol 5, 2779-2785, Copyright © 1985 by Society for Neuroscience
Immunoblot analysis of horseradish peroxidase conjugates of wheat germ agglutinin before and after retrograde transport in the rat peripheral nervous system
ML Schmidt and JQ Trojanowski
Immunoblot studies were performed on tissue extracts of rats injected with
horseradish peroxidase (HRP) conjugates of wheat germ agglutinin (WGA)
using anti-HRP and anti-WGA antisera. Immunoblots of uninjected, purified
conjugates (WGA-HRP) demonstrated a 62-kilodalton (kd) conjugate (monomeric
WGA conjugated to HRP). Other prominent immunobands included HRP (40 kd),
monomeric WGA (22 kd), and 15- to 30- kd HRP breakdown products. Following
injections of WGA-HRP into the submandibular gland of rats which survived
16 hr to 8 days, immunoblots were performed on homogenates of injected
submandibular glands and of superior cervical ganglia containing neurons
retrogradely labeled with WGA-HRP. The anti-HRP antiserum detected
unconjugated, 40-kd HRP and a 62-kd immunoband corresponding to WGA-HRP in
the superior cervical ganglia and submandibular glands. No immunobands were
detected with the antiserum to WGA in superior cervical ganglia
homogenates. Blots of submandibular gland homogenates harvested 24 hr after
a WGA-HRP injection, but not at later time points, contained an immunoband
reactive with the anti-WGA antiserum; it corresponded to monomeric WGA.
These studies analyze for the first time the molecular composition of
WGA-HRP conjugates before and after retrograde transport; they provide a
novel approach for probing the intraneuronal transport and degradation of
proteins. We conclude that morphologically defined endocytic pathways using
protein markers reflect the endocytosis and transport of immunochemically
altered and unaltered forms of the markers.