CONSTITUTIVE EXPRESSION OF THE 27-KDA HEAT-SHOCK-PROTEIN (HSP27) IN SENSORY AND MOTOR-NEURONS OF THE RAT NERVOUS-SYSTEM

In this study, the constitutive expression of the 27-kDa heat shock pr otein (Hsp27) in the adult rat central nervous system has been examine d by immunohistochemistry and by two-dimensional gel Western blot anal ysis. Hsp27 immunoreactivity was observed primarily in motoneurons of cranial nerve nuclei and spinal cord, and in primary sensory neurons a nd their central processes. Also, Hsp27 immunoreactivity was present i n neurons of the arcuate nucleus and of the reticular formation. Howev er, only a subset of these neurons was Hsp27-immunoreactive. Most gene ral somatic efferent motoneurons of the hypoglossal nucleus and spinal motor columns and most special visceral efferent motoneurons of the c ranial nerve nuclei were Hsp27-positive. In contrast, fewer general so matic efferent motoneurons for eye muscles were Hsp27-positive, and on ly a small proportion of general visceral efferent neurons, i.e., para sympathetic and sympathetic preganglionic neurons, were stained for Hs p27. Many pseudounipolar sensory neurons were Hsp27-immunoreactive, an d the patterns of staining in central sensory nuclei suggested that sp ecific subpopulations of sensory neurons contained Hsp27. The cellular distribution of Hsp27 was uniform throughout the cytoplasm, including the perikaryon, axon and dendrites, the latter often exhibiting varic osities or beading in distal processes. Western blot analyses revealed that at least three phosphorylated isoforms of Hsp27 were present in the spinal cord. These results suggest that constitutively expressed H sp27 may be related to functional subpopulations of motoneurons and pr imary sensory neurons. (C) 1997 Wiley-Liss, Inc.