Developmental Changes of Cyclic Adenosine Monophosphate-Dependent Protein Kinase Activity during Spermatogenesis in the Mouse 1

Open Access
Publisher Website
Google Scholar
Abstract
Cyclic AMP-dependent protein kinase. activity was studied in germ cells at different stages of meiosis and spermiogenesis. A constant decrease in total protein kinase activity was detected in the soluble fraction of germ cells, during spermatogenic development. This decrease was not associated with a redistribution of phosphorylative activity to other compartments of the cell. DEAE-cellulose chromatography of the cytosol of pachytene spermatocytes and round spermatids demonstrated the presence of two isoenzymcs of protein kinase eluting at 35 mM KCl (Peak I) and 170 mM KCl (Peak II). A selective decrease in the amount of Peak I could be observed with the progress of spermatid development, and Peak II was the major form present in elongating spermatids. Peak II isoenzyme was the most abundant form of protein kinase also in the soluble fraction of epididymal spermatozoa. A similar developmental pattern was obtained when cyclic AMP binding activity, rather then phosphorylative activity, was measured after ion exchange chromatography of different germ cell soluble fractions. The two protein kinase isoenzymes of germ cells had characteristics similar to those described in other cells of the testis and other tissues. In particular, Peak I kinase was dissociated and activated by high salt concentration and basic proteins, while Peak II kinase was insensitive to these treatments. These distinctive properties of the two isoenzymes were used to measure the relative concentration of the two forms directly in the crude cytosol preparations of germ cells. Pachytene spermazocyte kinase activity was dissociated by high salt to a level comparable to that of round spermatids. The soluble kinase present in elongating spermatids was, instead, insensitive to salt treatment, confirming the hypothesis that most of the activity present in this cell type has the characteristic of Peak II.