PROTEIN-PHOSPHORYLATION PATTERNS DURING ESTIVATION IN THE LAND SNAIL OTALA-LACTEA

Protein phosphorylation patterns were investigated in whole tissues an d subcellular fractions of active and aestivating Otala lactea (Muller ) (Pulmonata, Helicidae). Measurement of overall protein phosphorylati on showed that incorporation of P-32 increased until the second day af ter injection and remained constant for the remaining 4 days of the ti me course. Comparison of tissues from aestivating and active snails on day 3 showed a decreased protein phosphorylation in aestivating snail s (44% of active). No differences in total and protein-associated radi oactivity for foot, mantle or haemolymph were observed. Subcellular fr actionation of the hepatopancreas localized the changes to plasma memb rane, microsomal, and cytosolic fractions: values for aestivating anim als were reduced to 71, 37 and 58% of the corresponding active values. Separation of the individual subcellular fractions on isoelectric foc using columns revealed differences in the phosphate incorporation patt erns. Plasma membrane from aestivating animal hepatopancreas had a low er overall level of incorporation and fewer radioactive peaks in the p H 7-10 region than did the plasma membrane fraction from active animal s. SDS-PAGE analysis of plasma membrane fractions from active and aest ivating snails showed a relative decrease in phosphorylation between 6 0-80 kDa and 30-40 kDa. IEF analysis of cytosolic proteins from aestiv ating snail hepatopancreas also showed peaks of radioactivity that wer e apparently shifted by 0.3 pH units toward higher pi values. Increase d phosphate incorporation was observed at a peak that corresponded to the pi value for pyruvate kinase in aestivating snails but definite as signment of peaks was not possible. SDS-PAGE analysis of cytosolic pro teins showed an aestivation-related decrease in relative protein phosp horylation between 30-35 kDa and 40-45 kDa. A relative increase in pho sphorylation during aestivation was observed for proteins between 16-2 2 kDa. Overall, the data indicate that snails dramatically alter their protein phosphorylation pattern in hepatopancreas during aestivation.