Accumulating evidence suggests that gender impacts the incidence, susceptibility and severity of several lung diseases. Gender also influences lung development and physiology. Data from both human and animal studies suggests that sex hormones may contribute to disease pathogenesis or serve as protective factors, depending on the disease involved. In this review, the influence of gender and sex hormones on lung development and pathology will be discussed, with specific emphasis on pulmonary fibrosis, asthma and cancer.

Na ؉ ͞H ؉ exchanger regulatory factor (NHERF)-1 and NHERF-2, two structurally related protein adapters containing tandem PSD-95͞ Discs large͞ZO-1 (PDZ) domains, were identified as essential factors for protein kinase A-mediated inhibition of the sodium-hydrogen exchanger, NHE3. NHERF-1 and NHERF-2 also bound other cellular targets including the sodium-phosphate cotransporter type IIa encoded by the NPT2 gene. Targeted disruption of the mouse NHERF-1 gene eliminated NHERF-1 expression in kidney and other tissues of the mutant mice without altering NHERF-2 levels in these tissues. NHERF-1 (؉͞؊) and (؊͞؊) male mice maintained normal blood electrolytes but showed increased urinary excretion of phosphate when compared with wild-type (؉͞؉) animals. Although the overall levels of renal NHERF-1 targets, NHE3 and Npt2, were unchanged in the mutant mice, immunocytochemistry showed that the Npt2 protein was aberrantly localized at internal sites in the renal proximal tubule cells. The mislocalization of Npt2 paralleled a reduction in the transporter protein in renal brushborder membranes isolated from the mutant mice. In contrast, NHE3 was appropriately localized at the apical surface of proximal tubules in both wild-type and mutant mice. These data suggested that NHERF-1 played a unique role in the apical targeting and͞or trafficking of Npt2 in the mammalian kidney, a function not shared by NHERF-2 or other renal PDZ proteins. Phosphate wasting seen in the NHERF-1(؊͞؊) null mice provided a new experimental system for defining the role of PDZ adapters in the hormonal control of ion transport and renal disease.

NHERF (Na+/H+ exchanger regulatory factor or NHERF-1) and E3KARP (NHE3 kinase A regulatory protein or NHERF-2) are structurally related protein adapters that are highly expressed in epithelial tissues. NHERF proteins contain two tandem PDZ domains and a C-terminal sequence that binds several members of the ERM (ezrin-radixin-moesin) family of membrane-cytoskeletal adapters. Although identified as a regulator of NHE3, recent evidence points to a broadening role for NHERF in the function, localization and/or turnover of G-protein coupled receptors, platelet-derived growth factor receptor and ion transporters such as CFTR, Na/Pi cotransporter, Na/HCO3 cotransporter and Trp (calcium) channels. NHERF also recruits non-membrane proteins such as the c-Yes/YAP-65 complex, members of the phospholipase Cbeta family and the GRK6A protein kinase to apical surface of polarized epithelial cells where they regulate or respond to membrane signals. While two distinct models have been proposed for NHERF's role in signal transduction, the common theme is NHERF's ability to bring together membrane and non-membrane proteins to regulate cell metabolism and growth. NHERF overexpression in human breast cancers and mutations in NHERF targets, such as CFTR and merlin, the product of Neurofibromatosis NF2 tumor suppressor gene, that impair NHERF binding suggest that aberrant NHERF function contributes to human disease.

Numerous animal studies have revealed significant effects of sex and sex hormones on normal lung development, lung physiology, and various lung diseases. The primary goal of this review is to summarize knowledge to date on the effects of sex and sex hormones on lung development, physiology, and disease in animals. Specific emphasis will be placed on fibrosis, allergic airway disease, acute lung injury models, respiratory infection, and lung toxicology studies.

NHERFs are the best-studied apical PDZ proteins that are highly expressed in epithelial cells. Molecular and cellular studies over the past decade show that NHERFs regulate the targeting or trafficking of ion transporters and other membrane proteins and transduce physiological and pathophysiological signals that regulate ion homeostasis in mammals.

These data suggest that estrogen receptor-alpha is a critical regulator of airway hyperresponsiveness in mice.

Neurabins are protein phosphatase-1 (PP1) targeting subunits that are highly concentrated in dendritic spines and post-synaptic densities. Immunoprecipitation of neurabin I and neurabin II/spinophilin from rat brain extracts sedimented PP1␥1 and PP1␣ but not PP1␤. In vitro studies showed that recombinant peptides representing central regions of neurabins also preferentially bound PP1␥1 and PP1␣ from brain extracts and associated poorly with PP1␤. Analysis of PP1 binding to chimeric neurabins suggested that sequences flanking a conserved PP1-binding motif altered their selectivity for PP1␤ and their activity as regulators of PP1 in vitro. Assays using recombinant PP1 catalytic subunits and a chimera of PP1 and protein phosphatase-2A indicated that the C-terminal sequences unique to the PP1 isoforms contributed to their recognition by neurabins. Collectively, the results from several different in vitro assays established the rank order of PP1 isoform selection by neurabins to be PP1␥1 > PP1␣ > PP1␤. This PP1 isoform selectivity was confirmed by immunoprecipitation of neurabin I and II from brain extracts from wild type and mutant PP1␥ null mice. In the absence of PP1␥1, both neurabins showed enhanced association with PP1␣ but not PP1␤. These studies identified some of the structural determinants in PP1 and neurabins that together contribute to preferential targeting of PP1␥1 and PP1␣ to the mammalian synapse.Protein phosphatase-1 (PP1), 1 a major eukaryotic protein serine/threonine phosphatase, is encoded by multiple genes in both plants and animals. Disruption of PP1 genes in fungi (1), fruit flies (2), and mice (3) suggested that PP1 isoforms encoded by individual genes control distinct but overlapping physiological functions. Three mammalian isoforms, PP1␣, PP1␤, and PP1␥1, are expressed in all tissues (4) with PP1␥2, an alternately spliced product of the PP1␥ gene, present predominantly in testes (5, 6). Immunocytochemistry using isoform-specific antibodies suggested that expression of PP1 isoforms varied in different brain regions where they are also localized to different subcellular compartments (6, 7). For example, PP1␤ was the predominant isoform associated with microtubules in the neuronal cell body, whereas PP1␥1 and PP1␣ were preferentially concentrated in dendritic spines (6,8). Furthermore, by analyzing endogenous PP1 movement during the cell cycle, Andreassen et al. (9) showed that the distribution of PP1 isoforms in cells was highly dynamic. This placed new emphasis on understanding the mechanisms that target individual PP1 isoforms to cellular organelles.Isolation of PP1 bound to skeletal muscle glycogen (10) and myosin (11) established the paradigm that regulatory or targeting subunits bound to PP1 catalytic subunits dictate the subcellular localization, substrate recognition, and hormonal control of PP1. The search for PP1 regulators that control functions as diverse as protein synthesis, gene expression, cell division, and motility has thus far yielded more than 50 PP1-binding proteins (12). Wh...

The roles of sex hormones as modulators of lung function and disease have received significant attention as differential sex responses to various lung insults have been recently reported. The present study used a bleomycin-induced pulmonary fibrosis model in C57BL/6 mice to examine potential sex differences in physiological and pathological outcomes. Endpoints measured included invasive lung function assessment, immunological response, lung collagen deposition, and a quantitative histological analysis of pulmonary fibrosis. Male mice had significantly higher basal static lung compliance than female mice (P , 0.05) and a more pronounced decline in static compliance after bleomycin administration when expressed as overall change or percentage of baseline change (P , 0.05). In contrast, there were no significant differences between the sexes in immune cell infiltration into the lung or in total lung collagen content after bleomycin. Total lung histopathology scores measured using the Ashcroft method did not differ between the sexes, while a quantitative histopathology scoring system designed to determine where within the lung the fibrosis occurred indicated a tendency toward more fibrosis immediately adjacent to airways in bleomycin-treated male versus female mice. Furthermore, castrated male mice exhibited a female-like response to bleomycin while female mice given exogenous androgen exhibited a male-like response. These data indicate that androgens play an exacerbating role in decreased lung function after bleomycin administration, and traditional measures of fibrosis may miss critical differences in lung function between the sexes. Sex differences should be carefully considered when designing and interpreting experimental models of pulmonary fibrosis in mice.