Genetic variants in Nogo receptor signaling pathways may be associated with early life adversity in schizophrenia susceptibility
BBA CLINICAL
Authors: Andrews, Jessica L.; Fernandez-Enright, Francesca
Abstract
Background: Schizophrenia is a severe neuropsychiatric disorder thought to result from abnormal brain development. Nogo, an oligodendrocyte bound molecule, signals by binding to the Nogo receptor (NgR) located on axonal membranes. The NgR co-receptors include p75 neurotrophin receptor or TNF receptor orphan Y (TROY). Nogo signaling is responsible for central nervous system myelin regulation and neurite outgrowth during neurodevelopment, and plasticity in the mature brain. Methods: We examined single nucleotide polymorphisms (SNPs) in NgR, p75, and TROY receptor genes and downstream signaling partner With No Lysine (K) (WNK1) and Myelin transcription factor 1-like (Myt1l) genes in an Australian case-control schizophrenia cohort (n = 268/group). High-throughput SNP genotyping was performed using the MassARRAY (R) genotyping assay. Results: Analysis revealed a significant association between the Myt1l SNP rs2304008 and female schizophrenia subjects. The WNK1 SNP rs1468326 and the Myt1l SNP rs3748988 showed significant associations with schizophrenia in subjects with a maternal mental history and in subjects who experienced childhood trauma respectively. Following Bonferroni correction, all significance was lost. Conclusions: Despite the lack of positive findings in our population after correction for multiple testing, previous gene expression and association studies in schizophrenia suggest the implication of NgR signaling pathway genes in the etiology of schizophrenia remains topical and timely. General significance: Further investigations will be necessary to fully assess the role of these genes in the pathophysiology of schizophrenia. However these genes may prove useful in further understanding the mechanism by which negative experiences early in life can affect myelin-related processes in the context of schizophrenia. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Angiotensin II signaling via protein kinase C phosphorylates Kelch-like 3, preventing WNK4 degradation
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Authors: Shibata, Shigeru; Arroyo, Juan Pablo; Castaneda-Bueno, Maria; Puthumana, Jeremy; Zhang, Junhui; Uchida, Shunya; Stone, Kathryn L.; Lam, TuKiet T.; Lifton, Richard P.
Abstract
Hypertension contributes to the global burden of cardiovascular disease. Increased dietary K+ reduces blood pressure; however, the mechanism has been obscure. Human genetic studies have suggested that the mechanism is an obligatory inverse relationship between renal salt reabsorption and K+ secretion. Mutations in the kinases with-no-lysine 4 (WNK4) or WNK1, or in either Cullin 3 (CUL3) or Kelch-like 3 (KLHL3)-components of an E3 ubiquitin ligase complex that targets WNKs for degradation-cause constitutively increased renal salt reabsorption and impaired K+ secretion, resulting in hypertension and hyperkalemia. The normal mechanisms that regulate the activity of this ubiquitin ligase and levels of WNKs have been unknown. We posited that missense mutations in KLHL3 that impair binding of WNK4 might represent a phenocopy of the normal physiologic response to volume depletion in which salt reabsorption is maximized. We show that KLHL3 is phosphorylated at serine 433 in the Kelch domain (a site frequently mutated in hypertension with hyperkalemia) by protein kinase C in cultured cells and that this phosphorylation prevents WNK4 binding and degradation. This phosphorylation can be induced by angiotensin II (AII) signaling. Consistent with these in vitro observations, AII administration to mice, even in the absence of volume depletion, induces renal KLHL3(S433) phosphorylation and increased levels of both WNK4 and the NaCl cotransporter. Thus, AII, which is selectively induced in volume depletion, provides the signal that prevents CUL3/KLHL3-mediated degradation of WNK4, directing the kidney to maximize renal salt reabsorption while inhibiting K+ secretion in the setting of volume depletion.