Lipid rafts/caveolae are membrane platforms for signaling molecules that regulate various cellular functions, including cell survival. To better understand the role of rafts in tumor progression and therapeutics, we investigated the effect of raft disruption on cell viability and compared raft levels in human cancer cell lines versus their normal counterparts. Here, we report that cholesterol depletion using methyl-beta cyclodextrin caused anoikis-like apoptosis, which in A431 cells involved decreased raft levels, Bcl-xL down-regulation, caspase-3 activation, and Akt inactivation regardless of epidermal growth factor receptor activation. Cholesterol repletion replenished rafts on the cell surface and restored Akt activation and cell viability. Moreover, the breast cancer and the prostate cancer cell lines contained more lipid rafts and were more sensitive to cholesterol depletion-induced cell death than their normal counterparts. These results indicate that cancer cells contain increased levels of rafts and suggest a potential use of raft-modulating agents as anti-cancer drugs.

BackgroundDementia has been associated with an increased risk of hip fracture. However, little research has been conducted on the impact of dementia on wrist or vertebral fracture development. The aim of this study was to investigate whether dementia is a risk factor for different types of fracture in Taiwan.MethodsThe study sample was drawn from Taiwan’s National Health Insurance Research Database of reimbursement claims, and comprised 1408 patients who visited ambulatory care centers or were hospitalized with a diagnosis of dementia. The comparison group consisted of 7040 randomly selected individuals. Cox proportional hazard regression model was used to examine associations between dementia and the risk of different types of fracture.ResultsDuring a 3-year follow-up period, 264 patients with dementia (18.75%) and 1098 patients without dementia (15.60%) developed fractures. Dementia was independently associated with increased risk of hip fracture [adjusted hazard ratio (HR) 1.92, 95% CI 1.48–2.49]. Patients with dementia and osteoporosis had the highest risk of developing hip fracture (adjusted HR 2.27, 95% CI 1.28–4.01). Dementia did not increase wrist fracture or vertebral fracture risk when compared to the control group, even in patients with osteoporosis.ConclusionsIndividuals with dementia are at greater risk of developing hip fracture, particularly if they also have osteoporosis. Early mental screening programs and health education should be initiated to decrease disability and dependence in patients with dementia.

Caveolae (lipid rafts), microdomains of the plasma membrane, are known to contain various signalling molecules and consequently are involved in the regulation of many biological functions. To investigate the role of the caveolae in cell survival and adhesion, we disrupted the caveolae by depletion of cholesterol, a major lipid component of the caveolae, with methyl-beta cyclodextrin (MbetaCD) treatment of A431 cells. We found that cholesterol depletion induced an anoikis-like cell death involving actin reorganization, resulting in a decrease in cell spreading and an increase in cell detachment, which was reversed by cholesterol addition. Disruption of caveolae led to the down-regulation of FAK, Src activation, tyrosine phosphorylation of caveolin-1 and mobilization of caveolae markers, GM1 and caveolin-1, from the cell surface to the cytoplasm, which were also recovered by cholesterol addition. The expression of dominant-active FAK was able to delay caveolae internalization and apoptosis and attenuated Akt inactivation by MbetaCD, whereas dominant-negative FAK expression resulted in enhanced apoptosis. Moreover, FAK down-regulation by si-RNA resulted in Akt inactivation and thus increased cell death by MbetaCD treatment. Our results suggest that the cholesterol content and/or surface levels of the caveolae affect the activity of FAK, which in turn regulates caveolae internalization and cell survival.

In fission yeast, Scd1͞Ral1 is a putative guanine nucleotide exchange factor for Cdc42sp and also acts as a Ras1 effector necessary for the regulation of cytoskeleton organization. In this study, we have characterized a protein, Moe1, that binds directly to Scd1. A moe1 null (⌬) mutant exhibits numerous phenotypes indicative of abnormal microtubule functioning, including an abnormality in the spindle. moe1⌬ mutants are resistant to microtubule destabilizing agents; moreover, moe1⌬ rescued the growth defects of tubulin mutants containing unstable microtubules. These results suggest that Moe1 induces instability in microtubules. Biochemical and subcellular localization studies suggest that Moe1 and Scd1 colocalize in the nucleus. Furthermore, loss of function in Scd1 or Ras1 also induced abnormality in the spindle and is synthetically lethal with moe1⌬ producing cells that lack a detectable spindle. These data demonstrate that Moe1 is a component of the Ras1 pathway necessary for proper spindle formation in the nucleus. Human and nematode Moe1 both can substitute for yeast Moe1, indicating that the function of Moe1 in spindle formation has been conserved substantially during evolution.