The Journal of Neuroscience, February 1, 2001, 21(3):875-883
Golgi Complex, Endoplasmic Reticulum Exit Sites, and
Microtubules in Skeletal Muscle Fibers Are Organized by Patterned
Activity
Evelyn
Ralston1,
Thorkil
Ploug2,
John
Kalhovde3, and
Terje
Lømo3
1 Laboratory of Neurobiology, National
Institute of Neurological Disorders and Stroke, National Institutes of
Health, Bethesda, Maryland 20892-4062, 2 Copenhagen Muscle
Research Centre, Department of Medical Physiology, Panum Institute,
Copenhagen N, DK-2200 Denmark, and 3 Department of
Physiology, University of Oslo, Blindern N-0317, Norway
The Golgi complex of skeletal muscle fibers is made of thousands of
dispersed elements. The distributions of these elements and of the
microtubules they associate with differ in fast compared with slow and
in innervated compared with denervated fibers. To investigate the role
of muscle impulse activity, we denervated fast extensor digitorum
longus (EDL) and slow soleus (SOL) muscles of adult rats and stimulated
them directly with patterns that resemble the impulse patterns of
normal fast EDL (25 pulses at 150 Hz every 15 min) and slow SOL (200 pulses at 20 Hz every 30 sec) motor units. After 2 weeks of denervation
plus stimulation, peripheral and central regions of muscle fibers were
examined by immunofluorescence microscopy with regard to density and
distribution of Golgi complex, microtubules, glucose transporter GLUT4,
centrosomes, and endoplasmic reticulum exit sites. In
extrajunctional regions, fast pattern stimulation preserved normal fast
characteristics of all markers in EDL type IIB/IIX fibers, although
inducing changes toward the fast phenotype in originally slow type I
SOL fibers, such as a 1.5-fold decrease of the density of Golgi
elements at the fiber surface. Slow pattern stimulation had converse
effects such as a 2.2-fold increase of the density of Golgi elements at the EDL fiber surface. In junctional regions, where fast and slow fibers are similar, both stimulation patterns prevented a
denervation-induced accumulation of GLUT4. The results indicate that
patterns of muscle impulse activity, as normally imposed by motor
neurons, play a major role in regulating the organization of Golgi
complex and related proteins in the extrajunctional region of muscle fibers.
Key words:
muscle; Golgi complex; microtubules; plasticity; patterned activity; denervation
Copyright © 2001 Society for Neuroscience 0270-6474/01/213875-09$05.00/0
Previous Article | Next Article
