Growth and cell cycle abnormalities of fibroblasts from Tangier disease patients

We have investigated the abnormal proliferation and morphology of fibroblas ts from patients with Tangier disease (TD), a high density lipoprotein (HDL ) deficiency syndrome that is characterized by impairment of HDL3-mediated lipid efflux and G(i)-protein-mediated signaling via phosphatidylinositol-s pecific phospholipase C (PI-PLC) and phospholipase D (PLD). TD fibroblasts displayed a 30% to 50% reduced in vitro growth rate and a 1.6-fold increase d cell surface area. The response to different mitogens was diminished, and asynchronously growing TD fibroblasts showed 4.4+/-0.3% S-phase and 19.1+/ -0.5% G(2)/M-phase cells compared with 9.7+/-0.6% and 7.8+/-0.5%, respectiv ely, in controls. Monensin, but not brefeldin A, induced an S- and G(2)/M-p hase distribution in control cells similar to that found in TD fibroblasts. This effect of monensin was accompanied by an increase of ceramide levels in controls, whereas TD fibroblasts already had a 2.5-fold increased basal ceramide concentration. Incubation of control cells with C2 ceramide and th reo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) mimicked the ef fect of monensin on the cell cycle. The inhibition of neither Gi protein fu nction by pertussis toxin nor PLD by butanol resulted in a G(2)/M-phase arr est. Propranolol, known to increase phosphatidic acid levels, was ineffecti ve in reversing the G(2)/M-phase arrest in TD fibroblasts. in addition, cDN A sequences and mRNA expression of the participants of PI-PLC or PLD signal ing, ie, G-protein subunits alpha(i)1, alpha(i)2, and alpha(i)3; phosphatid ylinositol transfer proteins-alpha and -beta; and ADP ribosylation factors I and 3 were found to be normal. Thus, growth and cell cycle abnormalities in TD fibroblasts are likely to be related to impaired Golgi function and s phingolipid signaling rather than inoperative G-protein signal transduction . Because PDMP was also found to decrease HDL3-mediated lipid efflux in con trol but not TD fibroblasts, similar pathways seem to be involved in the di sturbances of lipid transport and growth retardation.