Protein kinase C-dependent inhibition of the lysosomal degradation

LAROCCA, M.C.; OCHOA , E.J.; RODRIGUEZ GARAY, E.A.; MARINELLI, R.A.

CELLULAR SIGNALLING

Elsevier

Año: 2002 vol. 14 p. 641 - 647

0898-6568

We studied the role of protein kinase C (PKC) in the lysosomal processing of endocytosed proteins in isolated rat hepatocytes. We used [14C]sucrose-labeled horseradish peroxidase ([14C]S-HRP) to simultaneously evaluate endocytosis and lysosomal proteolysis. The PKC activator phorbol 12-myristate 13-acetate (PMA) inhibited the lysosomal degradation of [14C]S-HRP (1 mM PMA: 40% inhibition, P < .05), without affecting either the endocytic uptake or the delivery to lysosomes. However, PMAwas not able to affect the lysosomal processing of the b-galactosidase substrate dextran galactosyl umbelliferone. The PKC inhibitors, chelerytrine (Che), staurosporine (St) and Go¨ 6976, prevented PMA inhibitory effect on lysosomal proteolysis. Nevertheless, purified PKC failed to alter proteolysis in [14C]S-HRP-loaded isolated lysosomes, suggesting that intracellular intermediates are required. PMA induced phosphorylation and hepatocyte membrane-tolysosome redistribution of the myristoylated alanine-rich C kinase substrate (MARCKS) protein, raising the possibility that MARCKS mediates the PKC-induced inhibition of lysosomal proteolysis. 14C]sucrose-labeled horseradish peroxidase ([14C]S-HRP) to simultaneously evaluate endocytosis and lysosomal proteolysis. The PKC activator phorbol 12-myristate 13-acetate (PMA) inhibited the lysosomal degradation of [14C]S-HRP (1 mM PMA: 40% inhibition, P < .05), without affecting either the endocytic uptake or the delivery to lysosomes. However, PMAwas not able to affect the lysosomal processing of the b-galactosidase substrate dextran galactosyl umbelliferone. The PKC inhibitors, chelerytrine (Che), staurosporine (St) and Go¨ 6976, prevented PMA inhibitory effect on lysosomal proteolysis. Nevertheless, purified PKC failed to alter proteolysis in [14C]S-HRP-loaded isolated lysosomes, suggesting that intracellular intermediates are required. PMA induced phosphorylation and hepatocyte membrane-tolysosome redistribution of the myristoylated alanine-rich C kinase substrate (MARCKS) protein, rising the possibility that MARCKS mediates the PKC-induced inhibition of lysosomal proteolysis. 14C]sucrose-labeled horseradish peroxidase ([14C]S-HRP) to simultaneously evaluate endocytosis and lysosomal proteolysis. The PKC activator phorbol 12-myristate 13-acetate (PMA) inhibited the lysosomal degradation of [14C]S-HRP (1 mM PMA: 40% inhibition, P < .05), without affecting either the endocytic uptake or the delivery to lysosomes. However, PMAwas not able to affect the lysosomal processing of the b-galactosidase substrate dextran galactosyl umbelliferone. The PKC inhibitors, chelerytrine (Che), staurosporine (St) and Go¨ 6976, prevented PMA inhibitory effect on lysosomal proteolysis. Nevertheless, purified PKC failed to alter proteolysis in [14C]S-HRP-loaded isolated lysosomes, suggesting that intracellular intermediates are required. PMA induced phosphorylation and hepatocyte membrane-tolysosome redistribution of the myristoylated alanine-rich C kinase substrate (MARCKS) protein, rising the possibility that MARCKS mediates the PKC-induced inhibition of lysosomal proteolysis.