Tyrosine phosphatase inhibitor triggers rodlet cell discharge in sunfish scale epidermis cultures

Abstract

AbstractEpidermal rodlet cells were evaluated after treatment with the tyrosine phosphatase inhibitor pervanadate. Treatment of sunfish explant cell cultures with the inhibitor triggered a contraction of the rodlet cells and expulsion of cell contents. Time‐lapse video differential interference contrast (DIC) microscopy was used to evaluate rodlet cell contraction and rodlet discharge. Three general steps in pervanadate triggered discharge were identified. First the rodlet cell undergoes a constriction of the midsection. Constriction is followed by a rapid forward movement of rodlets and sacs to the apical end of cell, culminating in discharge of rodlets and other cellular contents, including the nucleus. A ring‐shaped structure around the apical pore was identified with DIC microscopy. Fluorescent‐labeled phalloidin and antibodies to alpha‐actinin and phosphotyrosine strongly stained the apical ring. A diffuse granular staining for both antibodies was also observed throughout the fibrous capsule. The results suggest that tyrosine kinases play a role in rodlet cell contraction. Alpha‐actinin is a known substrate for tyrosine kinases and is a potential target for triggering rodlet cell contraction and rodlet ejection. Modification of alpha‐actinin tyrosines could also be a mechanism for regulating the structural integrity of the fibrous capsule.