THE EFFECTS OF COPPER ON ACTIN AND FIBRONECTIN ORGANIZATION IN MYTILUS-GALLOPROVINCIALIS HEMOCYTES

The effects of copper on actin and fibronectin organization in Mytilus galloprovincialis haemocytes were studied, The Cu2+ exposure of musse ls caused severe perturbations in haemocyte actin and fibronectin orga nization with respect to non-exposed organisms, Cytoskeletal actin was analysed by indirect immunofluorescence, using an anti-total actin mo noclonal antibody, and by rhodamine-conjugated phalloidin, The majorit y of haemocytes from Cu2+-exposed mussels displayed a round morphology , with short and blunt filopodia; they lacked the polarized phenotype which was typical in control samples, The cytoskeleton alteration, mor e evident after phalloidin staining, resulted in the disappearance of filamentous actin, The actin cortical meshwork also appeared disorgani zed, The cytoskeletal morphology studied by transmission electron micr oscopy after negative staining of Triton X-100-treated haemocytes conf irmed these observations. The structural organization of actin when an alysed by Western blotting showed a larger number of Triton-soluble ac tin pools in treated mussel haemocytes, Fibronectin was studied by ind irect immunofluorescence using a polyclonal antiserum directed against mussel fibronectin. In treated mussels, fibronectin appeared to be st rongly disorganized and its levels decreased in both haemocytes and ha emolymph, The mechanism(s) of the copper-induced alterations on actin and fibronectin organization in mussel immunocytes is discussed. Copyr ight (C) 1996 Elsevier Science Ltd.