Intracellular protein degradation and autophagy in isolated pancreatic acini of the rat

✍ Scribed by Agnes Telbisz; Attila L. Kovacs

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 329 KB
• Volume: 18
• Category: Article
• ISSN: 0263-6484
• DOI: 10.1002/(sici)1099-0844(200001/03)18:1<29::aid-cbf844>3.0.co;2-g

✦ Synopsis

Simultaneous investigation of protein degradation and autophagy of isolated exocrine pancreatic cells is carried out here for the ®rst time in a systematic way by a complex biochemical, morphological and morphometrical approach. Protein degradation proceeds with a decreasing rate of 4±1 . 5 per cent per h over a 4-h period indicating a comparatively low degradation capacity. Cells in freshly isolated acini do not contain autophagic vacuoles but the latter appear within an hour in vitro and their quantity remains close to a steady state during the subsequent 3 h. Both traditional inhibitors of the autophagic-lysosomal pathway, e.g. vinblastine, leupeptin, and lysosomotropic amines together with the recently introduced 3-methyladenine, inhibit degradation to a similar maximal extent, oering the possibility of the estimation of the ratio of lysosomal/non-lysosomal degradation. In pancreatic acinar cells autophagic sequestration is unaected and protein degradation is inhibited inside secondary lysosomes by leupeptin and lysosomotropic amines, while 3-methyladenine prevents the formation of autophagosomes. Vinblastine seems to act by inhibiting the fusion of autophagosomes with lysosomes and there is no evidence for the stimulation of autophagic sequestration by vinblastine in the present system. The eect of inhibitors of protein breakdown on protein synthesis is variable and does not correlate with their in¯uence on degradation. Amino acids strongly stimulate protein synthesis, but in contrast to what is found in liver cells, they do not seem to aect protein degradation or autophagy signi®cantly, thus indicating major regulatory dierences of these processes between pancreatic acinar cells and hepatocytes.