Spj. Brooks et Kb. Storey, PROTEIN-PHOSPHORYLATION PATTERNS DURING ESTIVATION IN THE LAND SNAIL OTALA-LACTEA, Molecular and cellular biochemistry, 143(1), 1995, pp. 7-13
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.