An interesting background paper:

1. HDAC6 Regulates Glucocorticoid Receptor Signaling inSerotonin Pathways with Critical Impact on Stress Resilience Julie Espallergues,1* Sarah L. Teegarden,1* Avin Veerakumar,1 Janette Boulden,1 Collin Challis,1 Jeanine Jochems,1 Michael Chan,1 Tess Petersen,1 Evan Deneris,3 Patrick Matthias,4 Chang-Gyu Hahn,1 Irwin Lucki,1 Sheryl G. Beck,2 and Olivier Berton1 1 Department of Psychiatry, University of Pennsylvania Medical School, and 2 Department of Anesthesiology, Children’s Hospital of Philadelphia Research Institute and University of Pennsylvania, Philadelphia, Pennsylvania 19104, 3 Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, and 4 Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland

2. An interesting background paper: Molecular Adaptations Underlying Susceptibility and Resistance to Social Defeat in Brain Reward Regions Background

3. Resistant mice: Social defeat Upregulated K channels Rescuing BDNF releasing Question: How to explain the prolonged depressive behaviors? What is the role of reward system associated with the social defeat? Background

4. Background knowledge about our main paper: Glucocorticoid Receptor(GR) & Mineralcorticoid receptor(MR) • Both bind with cortisol. • When they are not bond with hormones, they need chaperone proteins(hsp90, hsp70, FKBP52) to protect their structure. • MR binds when CORT is low(high affinity), can be seen as the threshold for stress responses. GR binds when CORT is high(low affinity), mediate most of stress behaviors. Background

5. Descending limb is associated with MR. Ascending limb is associated with GR. In DR, GR activates 5-HT1A receptor which is inhibitory. (same in our main paper) Background

6. Histone deacetylation and HDAC6 (Histone acetylase 6) Hsp90 is one of a substrate of HDAC6. Generally what happens is… Background

7. But in our main paper, they were talking about hsp90 as the chaperone protein… “We show that HDAC6 functions as an Hsp90 deacetylase. Inactivation of HDAC6 leads to Hsp90 hyperacetylation, its dissociation from an essential cochaperone, p23, and a loss of chaperone activity. In HDAC6-deficient cells, Hsp90-dependent maturation of the glucocorticoid receptor (GR) is compromised, resulting in GR defective in ligand binding, nuclear translocation, and transcriptional activation. “ Tso-Pang Yao 2005 Acetylated Hsp90 inhibits the functions of GR. Background

8. HDAC6 Regulates Glucocorticoid Receptor Signaling inSerotonin Pathways with Critical Impact on Stress Resilience Fig 1 : To make sure there were lots of HDAC6 in raphe

9. Fig 2: To make sure there were lots of HDAC6 in serotonin neuron Fig 3:Downregulated HDAC6 expression in the dorsal raphe of resilient and imipramine-treated mice (social defeat for 10d and imipramine injection for 28d)

10. Fig 4: Conditional ablation of HDAC6 in raphe neurons A very interesting method of genetic knockout used in fruit flies ---- Gal4/UAS

11. Fig 5: Serotonin-selective depletion of HDAC6 promotes an antidepressant-like phenotype in mice exposed to inescapable stress

12. Fig 6: Depletion of HDAC6 prevents social defeat-induced hypoexcitability of serotonin neurons (remember 5-HT1A receptors are inhibitory)

13. Fig 7: Depletion of HDAC6 prevents social defeat-induced hypertrophy of 5-HT neurons

14. GR agonist Fig 8: HDAC6 depletion leads to Hsp90 hyperacetylation and impaired GR chaperoning GR inhibitor GR inhibitor GR inhibitor

15. Fig 9: HDAC6 depletion prevents transcriptional and electrophysiological effects of glucocorticoids in 5-HT neurons

16. Fig 10: Serotonergic depletion of HDAC6 alters the socioaffective effects of glucocorticoid hormones CORT made KO mice hyper-locomotor?

17. Fig 11: The idea of this paper