Volume 86, Issue 4, Pages 757-767 (October 2014) Early targets of lithium in rat kidney inner medullary collecting duct include p38 and ERK1/2  Francesco Trepiccione, Trairak Pisitkun, Jason D. Hoffert, Søren B. Poulsen, Giovambattista Capasso, Søren Nielsen, Mark A. Knepper, Robert A. Fenton, Birgitte M. Christensen  Kidney International  Volume 86, Issue 4, Pages 757-767 (October 2014) DOI: 10.1038/ki.2014.107 Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 1 Summary of the phosphoproteomic profile. (a) The Venn diagram summarizes the distributions of the phosphopeptides as identified by the three employed searching algorithms, InSpecT, OMSSA, and SEQUEST. (b) The histogram shows the distribution of the relative abundance (QUOIL, label-free quantification) of the phosphopeptides reported as the log2 ratio of the LiCl to the NaCl-treated group. The vertical red line points at zero, and ±0.6. In (c), the MOTIF-X logo shows the most predominant amino acid residues surrounding the phosphorylated serine in the LiCl-upregulated phosphopeptides (log2 ratio ≥0.75). Kidney International 2014 86, 757-767DOI: (10.1038/ki.2014.107) Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 2 Relational network showing potential functional interactions among proteins whose phosphorylation changed in the inner medullary collecting duct in response to lithium administration for 9h. Network was identified in STRING 9.0 and displayed in Medusa 1.5. The analysis revealed two major clusters: an actin cluster and a CDC42 cluster. The hub proteins for these two clusters, inserted by the STRING software to increase overall connectivity, are shown as blue symbols. Proteins whose phosphorylation increased in response to lithium are indicated in red; those whose phosphorylation decreased are indicated in green. On the basis of prior literature (see text), two other proteins were added (black symbols): β-catenin and glycogen synthase kinase 3β. Protein kinases are indicated by circular symbols; all other proteins are indicated by square symbols. All proteins are designated by their official gene symbols. See Tables 2 and 3 for specific phosphorylation sites and their magnitudes of change. Kidney International 2014 86, 757-767DOI: (10.1038/ki.2014.107) Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 3 pS261-AQP2 are upregulated 9h after LiCl administration. Immunoblotting showed an upregulation of pS261-AQP2, whereas no changes were observed for pS256-AQP2 or total AQP2, 9h after a gavage of LiCl (308mmol/l, 2.4mmol/kg body weight). The blots only include paired samples used in the data analysis. Complete blots are shown in Supplementary Figure S1 online. The amount of pAQP2 was corrected for the amount of total AQP2. Bar graphs show densitometric quantification relative to the NaCl group. Data are shown as mean±s.e. n=7 in both groups, **P-value <0.01. Kidney International 2014 86, 757-767DOI: (10.1038/ki.2014.107) Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 4 pS261-AQP2 has a broad intracellular localization 9h after LiCl exposure. Representative images from the proximal (IM-1, a and b) and the middle (IM-2, c and d) part of renal inner medulla of rats treated with NaCl (a and c) or LiCl (b and d) 9h before fixation of kidneys. In both IM-1 and IM-2, LiCl-treated rats showed a broader intracellular localization of p261-AQP2 compared with NaCl-treated rats, which presented p261-AQP2 mainly at the apical plasma membrane domains (arrows, a and c). The LiCl-treated group also showed staining of basolateral plasma membrane domains (arrowheads, b and d). In general, the staining of pSer261-AQP2 was higher in the LiCl-treated animals compared with the controls. n=5 per group. Kidney International 2014 86, 757-767DOI: (10.1038/ki.2014.107) Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 5 pERK1/2 and pP38α are upregulated 4h after LiCl administration. Immunoblotting showed an upregulation of pERK1/2 and pP38α 4h after a gavage of LiCl. No variation in pJNK1/2 expression was observed 4h after LiCl treatment. The amount of phosphorylated protein was corrected for the amount of total protein. Bar graphs show densitometric quantification relative to the NaCl group. Data are shown as mean±s.e. n=8 in both groups. **P-value <0.01. Kidney International 2014 86, 757-767DOI: (10.1038/ki.2014.107) Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 6 MAPK inhibitor treatment prevents the Li+-induced upregulation of pS261-AQP2. Immunoblotting of IMCD samples from rats pretreated with MAPK inhibitors, pERK1/2 (PD0325901) and pP38α (SB203580) (10 and 20mg/kg body weight in 15% dimethyl sulfoxide (DMSO), respectively), or vehicle (15% DMSO) 1h before a gavage of LiCl (9h). The expression of pS261-AQP2 was significantly lower, whereas the expression of total AQP2 was significantly higher in the group treated with MAPK inhibitors. The amount of phosphorylated AQP2 was corrected for the amount of total AQP2. Bar graphs show densitometric quantification relative to the vehicle group. Data are shown as mean±s.e. n=8 in both groups. *P-value<0.05. Kidney International 2014 86, 757-767DOI: (10.1038/ki.2014.107) Copyright © 2014 International Society of Nephrology Terms and Conditions