Lipid raft-associated stomatin enhances cell fusion.

Membrane fusions that occur during vesicle transport, virus infection, and tissue development, involve receptors that mediate membrane contact and initiate fusion and effectors that execute membrane reorganization and fusion pore formation. Some of these fusogenic receptors/effectors are preferentially recruited to lipid raft membrane microdomains. Therefore, major constituents of lipid rafts, such as stomatin, may be involved in the regulation of cell-cell fusion. Stomatin produced in cells can be released to the extracellular environment, either through protein refolding to pass across lipid bilayer or through exosome trafficking. We report that cells expressing more stomatin or exposed to exogenous stomatin are more prone to undergoing cell fusion. During osteoclastogenesis, depletion of stomatin inhibited cell fusion but had little effect on tartrate-resistant acid phosphatase production. Moreover, in stomatin transgenic mice, increased cell fusion leading to enhanced bone resorption and subsequent osteoporosis were observed. With its unique molecular topology, stomatin forms molecular assembly within lipid rafts or on the appositional plasma membranes, and promotes membrane fusion by modulating fusogenic protein engagement.-Lee, J.-H., Hsieh, C.-F., Liu, H.-W., Chen, C.-Y., Wu, S.-C., Chen, T.-W., Hsu, C.-S., Liao, Y.-H., Yang, C.-Y., Shyu, J.-F., Fischer, W. B., Lin, C.-H. Lipid raft-associated stomatin enhances cell fusion.

Direct Adeno-associated Viruses Injection of Murine Adipose Tissue.

The adipose tissue is a central metabolic organ that regulates whole-body energy homeostasis. The abnormal expansion of adipose tissue leads to the progression of obesity. The adipose tissue microenvironment is affected by pathological hypertrophy of adipocytes, highly correlated with systemic metabolic disorders. In vivo genetic modification is a great tool for understanding the role of genes involved in such processes. However, obtaining new conventional engineered mice is time consuming and costly. Here, we provide a simple and speedy method to efficiently transduce genes into adipose tissue by injecting the adeno-associated virus vector serotypes 8 (AAV8) into the fat pads of adult mice.

In vitro assessment of reproductive toxicity of cigarette smoke and deleterious consequences of maternal exposure to its constituents.

Cigarette smoke is known to be a serious health risk factor and considered reproductively toxic. In the current study, we investigated whether constituents of cigarette smoke, pyrazine, 2-ethylpyridine, and 3-ethylpyridine, adversely affect reproductive functioning such as oocyte maturation and sperm capacitation. Our findings indicated that three smoke components were involved in retardation of oocyte maturation in a dose-dependent manner and the lowest-observed-adverse-effect level (LOAEL) was determined to be 10(-10)M. However, individual smoke components administrated at the LOAEL did not attenuate oocyte maturation, demonstrating that all three toxicants were equally required for the observed growth impairment. When exposed to all three components at 10(-10)M during in vitro capacitation, murine sperm lost forward progression and were unable to show adequate hyperactivation, which is indicative of the incompletion of the capacitation process. Only sperm administrated with 3-ethylpyridine alone showed significant reduction in capacitation status, suggesting the chemical is the one responsible for disrupting sperm capacitation. Taken together, this is the first report that documents the effect of cigarette smoke components on oocyte maturation and sperm capacitation. The present findings demonstrate the adverse effects of smoke constituents of mammalian reproduction and the differences in sensitivity to smoke components between male and female gametes. Since both processes take place in the female reproductive system, our data provide new insights into deleterious consequences of maternal exposure to cigarette smoke.

Stomatin modulates adipogenesis through the ERK pathway and regulates fatty acid uptake and lipid droplet growth.

Regulation of fatty acid uptake, lipid production and storage, and metabolism of lipid droplets (LDs), is closely related to lipid homeostasis, adipocyte hypertrophy and obesity. We report here that stomatin, a major constituent of lipid raft, participates in adipogenesis and adipocyte maturation by modulating related signaling pathways. In adipocyte-like cells, increased stomatin promotes LD growth or enlargements by facilitating LD-LD fusion. It also promotes fatty acid uptake from extracellular environment by recruiting effector molecules, such as FAT/CD36 translocase, to lipid rafts to promote internalization of fatty acids. Stomatin transgenic mice fed with high-fat diet exhibit obesity, insulin resistance and hepatic impairments; however, such phenotypes are not seen in transgenic animals fed with regular diet. Inhibitions of stomatin by gene knockdown or OB-1 inhibit adipogenic differentiation and LD growth through downregulation of PPARγ pathway. Effects of stomatin on PPARγ involves ERK signaling; however, an alternate pathway may also exist.

In vitro assessment of reproductive toxicity of cigarette smoke and deleterious consequences of maternal exposure to its constituents

Cigarette smoke is known to be a serious health risk factor and considered reproductively toxic. In the current study, we investigated whether constituents of cigarette smoke, pyrazine, 2-ethylpyridine, and 3-ethylpyridine, adversely affect reproductive functioning such as oocyte maturation and sperm capacitation. Our findings indicated that three smoke components were involved in retardation of oocyte maturation in a dose-dependent manner and the lowest-observed-adverse-effect level (LOAEL) was determined to be 10-10M. However, individual smoke components administrated at the LOAEL did not attenuate oocyte maturation, demonstrating that all three toxicants were equally required for the observed growth impairment. When exposed to all three components at 10-10M during in vitro capacitation, murine sperm lost forward progression and were unable to show adequate hyperactivation, which is indicative of the incompletion of the capacitation process. Only sperm administrated with 3-ethylpyridine alone showed significant reduction in capacitation status, suggesting the chemical is the one responsible for disrupting sperm capacitation. Taken together, this is the first report that documents the effect of cigarette smoke components on oocyte maturation and sperm capacitation. The present findings demonstrate the adverse effects of smoke constituents of mammalian reproduction and the differences in sensitivity to smoke components between male and female gametes. Since both processes take place in the female reproductive system, our data provide new insights into deleterious consequences of maternal exposure to cigarette smoke.