Cryo-EM structure of the potassium-chloride cotransporter KCC4 in lipid nanodiscs.

Cation-chloride-cotransporters (CCCs) catalyze transport of Cl- with K+ and/or Na+across cellular membranes. CCCs play roles in cellular volume regulation, neural development and function, audition, regulation of blood pressure, and renal function. CCCs are targets of clinically important drugs including loop diuretics and their disruption has been implicated in pathophysiology including epilepsy, hearing loss, and the genetic disorders Andermann, Gitelman, and Bartter syndromes. Here we present the structure of a CCC, the Mus musculus K+-Cl- cotransporter (KCC) KCC4, in lipid nanodiscs determined by cryo-EM. The structure, captured in an inside-open conformation, reveals the architecture of KCCs including an extracellular domain poised to regulate transport activity through an outer gate. We identify binding sites for substrate K+ and Cl- ions, demonstrate the importance of key coordinating residues for transporter activity, and provide a structural explanation for varied substrate specificity and ion transport ratio among CCCs. These results provide mechanistic insight into the function and regulation of a physiologically important transporter family.

Hypothalamic estrogen receptor alpha establishes a sexually dimorphic regulatory node of energy expenditure.

Estrogen receptor a (ERa) signaling in the ventromedial hypothalamus (VMH) contributes to energy homeostasis by modulating physical activity and thermogenesis. However, the precise neuronal populations involved remain undefined. Here, we describe six neuronal populations in the mouse VMH by using single-cell RNA transcriptomics and in situ hybridization. ERa is enriched in populations showing sex biased expression of reprimo (Rprm), tachykinin 1 (Tac1), and prodynorphin (Pdyn). Female biased expression of Tac1 and Rprm is patterned by ERa-dependent repression during male development, whereas male biased expression of Pdyn is maintained by circulating testicular hormone in adulthood. Chemogenetic activation of ERa positive VMH neurons stimulates heat generation and movement in both sexes. However, silencing Rprm gene function increases core temperature selectively in females and ectopic Rprm expression in males is associated with reduced core temperature. Together these findings reveal a role for Rprm in temperature regulation and ERa in the masculinization of neuron populations that underlie energy expenditure.

Estrogen signaling in arcuate Kiss1 neurons suppresses a sex-dependent female circuit promoting dense strong bones.

Central estrogen signaling coordinates energy expenditure, reproduction, and in concert with peripheral estrogen impacts skeletal homeostasis in females. Here, we ablate estrogen receptor alpha (ERα) in the medial basal hypothalamus and find a robust bone phenotype only in female mice that results in exceptionally strong trabecular and cortical bones, whose density surpasses other reported mouse models. Stereotaxic guided deletion of ERα in the arcuate nucleus increases bone mass in intact and ovariectomized females, confirming the central role of estrogen signaling in this sex-dependent bone phenotype. Loss of ERα in kisspeptin (Kiss1)-expressing cells is sufficient to recapitulate the bone phenotype, identifying Kiss1 neurons as a critical node in this powerful neuroskeletal circuit. We propose that this newly-identified female brain-to-bone pathway exists as a homeostatic regulator diverting calcium and energy stores from bone building when energetic demands are high. Our work reveals a previously unknown target for treatment of age-related bone disease.

Acculturation and smoking in North Americans of Chinese ancestry: A systematic review.

OBJECTIVES: Many North American immigrants come from China. Given the critical impact of tobacco use on health, it is important to understand rates and correlates of smoking in this population. This systematic review addressed the question: based on current research, what is the association between acculturation and smoking behaviours in Chinese immigrants to North America? METHODS: The search was conducted in PubMed, Medline, Web of Science, and Academic Search Complete for papers published from 2005 to 2014. Data were extracted from Canadian and American studies for population characteristics, study design, measures of smoking and acculturation, and findings regarding smoking rates and associations between smoking and acculturation. SYNTHESIS: The literature search identified 147 articles, and 14 met inclusion criteria. Three studies were based on Canadian samples and the remaining 11 were from the United States. Of the 14 papers, 3 reported findings for youth and 11 for adults. Among adults, daily smoking rates were consistently much higher in men than women; for men, rates varied from 9% to 30%. Language use and time in North America were the most common indicators of acculturation. Almost all studies found a relationship between acculturation and smoking, such that more acculturated men smoke less and more acculturated women smoke more. CONCLUSION: The findings suggest that the association between acculturation and smoking is gender-specific. This correlation is found in youth and adults and in both Canada and the US. Increased acculturation has a protective effect on smoking for Chinese North American men, but a harmful effect for women. Tobacco control interventions need to develop targeted strategies appropriate to these different populations.