Characterization of 5-HT receptor and transport protein KIF13A expression in the hippocampus of stress-adaptive and -maladaptive mice.

The ability to adapt to stress is an essential defensive function of a living body, and disturbance of this ability in the brain may contribute to the development of affective illness including major depression and anxiety disorders. A growing body of evidence suggests that brain serotonin (5-HT) receptors may be involved, at least in part, in the development of adaptation to stress. 5-HT receptor was reported to be transported by KIF13A, a motor protein and a member of the kinesin superfamily, from the golgi apparatus to the plasma membrane. The aim of the present study was to characterize the expression pattern of 5-HT receptor and KIF13A in the hippocampus of stress-adaptive and -maladaptive mice. Mice were either exposed to repeated adaptable (1 h/day) or unadaptable (4 h/day) restraint stress, or left in their home cage for 14 days. The levels of 5-HT receptor and KIF13A expression were assessed by western blot analysis. To confirm the formation of a 5-HT receptor and KIF13A complex, we performed blue native-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (BN-SDS-PAGE). Western blotting showed that neither 5-HT receptor nor KIF13A expression changed significantly in the hippocampal total extract of stress-adaptive and -maladaptive mice. In contrast, expression of 5 H T receptor and KIF13A in the hippocampal membrane fraction was increased in stress-adaptive mice, but not in stress-maladaptive mice. BN-SDS-PAGE analysis revealed that the bands of 5-HT receptor and KIF13A were both observed at a molecular weight of approximately 70 kDa, which indicated that 5-HT receptor and KIF13A form a complex. The present findings suggest that translocation of 5-HT receptor in complex with KIF13A to the plasma membrane of the hippocampus may play an important role in the formation of stress adaptation.