Overexpression of amyloid precursor protein increases copper content in HEK293 cells

Amyloid precursor protein (APP) is a transmembrane glycoprotein widely expressed in mammalian tissues and plays a central role in Alzheimer’s disease. However, its physiological function remains elusive. Cu²⁺ binding and reduction activities have been described in the extracellular APP135-156 region, which might be relevant for cellular copper uptake and homeostasis. Here, we assessed Cu²⁺ reduction and ⁶⁴Cu uptake in two human HEK293 cell lines overexpressing APP. Our results indicate that Cu²⁺ reduction increased and cells accumulated larger levels of copper, maintaining cell viability at supra-physiological levels of Cu²⁺ ions. Moreover, wild-type cells exposed to both Cu²⁺ ions and APP135-155 synthetic peptides increased copper reduction and uptake. Complementation of function studies in human APP751 transformed Fre1 defective Saccharomyces cerevisiae cells rescued low Cu²⁺ reductase activity and increased ⁶⁴Cu uptake. We conclude that Cu²⁺ reduction activity of APP facilitates copper uptake and may represent an early step in cellular copper homeostasis.     

An experimental investigation of enhanced harpacticoid (Copepoda) abundances around isolated seagrass shoots

Summary Premature leaf abscission in Populus was observed in central Washington (USA) about two weeks after the 18 May 1980 ashfall from Mount St. Helens. Leaf abscission was probably a wounding response caused by sandsized ash carried in winds that gusted to 15 m s^-1 7 days after the ashfall. Under glasshouse conditions simulating this environmental regime the leaf epidermis and often part of the mesophyll in Populus nigra L. var. italica Duroi. were abraded, resulting in permanent loss of leaf turgor and decreased stomatal conductance. Substantial abscission of still-green leaves ensued. Leaf abrasion by ash-laden winds, although rare, may result in conspicuous plant damage.