Intracellular localization of heat shock mRNAs (hsc70 and hsp70) to neural cell bodies and processes in the control and hyperthermic rabbit brain

Heat shock proteins are essential cellular proteins that may play important roles in cellular repair and/or protection. This report focuses on the expression of two members of the hsp70 multigene family, namely, constitutive hsc70 mRNA and stress-inducible hsp70 mRNA in the control and hyperthermic rabbit brain. The intracellular localization of these heat shock mRNAs was examined using high-resolution nonradioactive in situ hybridization. The distribution of hsc70 mRNA and hsp70 mRNA was examined in (1) neuronal cell bodies and their dendritic processes and (2) oligodendrocytes and their cellular processes. In control animals, hsc70 mRNA was detected in the apical dendritic processes and cell bodies of cortical layer II and V neurons, CA3 and CA4 neurons, deep cerebellar neurons, and brainstem neurons. A time course analysis of hsc70 mRNA, after a physiologically relevant increase in body temperature of 2.6 degrees C, revealed more distal transport of this constitutive message into dendrites of these neuronal populations. In the same neuronal populations, basal levels of hsp70 mRNA were observed in the cell body; however, this mRNA was not detected in dendritic processes in control or hyperthermic animals. After hyperthermia, hsp70 mRNA was strongly induced in oligodendrocytes and transported to the processes of these glial cells. The localization of heat shock messages in the processes of these neural cell types could provide a mechanism for local control of synthesis of heat shock proteins in cellular compartments that are remote from the cell body.