Search

To investigate whether the observed association of intracellular neuronal calcium sensor (NCS) proteins with amyloid plaques and neurofibrillar tangles in Alzheimer brains is linked to a possible neuroprotective or neurotoxic activity of the protein, we performed cytotoxicity tests in PC12 cells transfected with the calcium sensor protein VILIP-1 (visinin-like protein) and the calcium buffer protein calbindin-D28K. Whereas VILIP-1 expression enhanced the neurotoxic effect of ionomycin already at low ionophore concentrations, calbindin-D28K protected against ionomycin-induced cytotoxicity only at high ionomycin and therefore calcium concentrations. However, in double-transfected cells calbindin-D28K rescued VILIP-1-mediated cytotoxicity at low ionomycin concentrations. Since VILIP-1 was found to be associated with fibrillar tangles in Alzheimer brains, we tested whether VILIP-1 has an influence on tau hyperphosphorylation. VILIP-1 expression enhanced hyperphosphorylation of tau protein compared to nontransfected or calbindin-D28K-transfected cells. These results raise the possibility that the observed reduction in VILIP-1-expressing cells may indicate a selective vulnerability of these neurons and that the calcium sensor protein is involved in the pathophysiology of Alzheimer's disease. The calcium sensor protein may influence tau phosphorylation and have a role in calcium-mediated neurotoxicity opposed to the previously discovered protective effect of calcium buffer proteins.

Injured areas of the respiratory epithelium are subject to rapid repair by the migration of adjacent epithelial cells, a process termed "restitution". Rapid re-epithelialization is promoted by interactions between migrating cells and the extracellular matrix proteins. Furthermore, epidermal growth factor (EGF) as well as trefoil factor family (TFF) peptides are well known regulators of epithelial restitution due to their motogenic effects. Migration of the human bronchial epithelial cell line BEAS-2B in modified Boyden chambers was used as a model system for airway restitution. EGF or recombinant human TFF2 or TFF3 showed mainly chemotactic activity. The motogenic response was strictly dependent upon a haptotactic substrate, but to different degrees. EGF induced phosphorylation of extracellular signal-regulated kinases (ERK) 1/2, c-Jun-N-terminal kinase, p38, Akt, and p70S6K in BEAS-2B cells. Using specific inhibitors, the signaling cascades responsible for the motogenic response were shown to differ drastically when EGF was compared with TFF2. The motogenic effect of TFF2 was previously demonstrated to depend on ERK1/2 and protein kinase C activation; whereas the EGF-triggered motogenic response was completely independent of ERK1/2 activation but sensitive to the inhibition of phosphoinositide 3-kinase, p38, protein kinase C, or nuclear factor kappaB. However, the motogenic effects of EGF and TFF2 are additive. These data suggest that luminal EGF and TFF peptides can act synergistically in the human respiratory epithelium to enhance rapid repair processes in the course of diseases such as asthma.