Inactivation of the three GGA genes in HeLa cells partially compromises lysosomal enzyme sorting

FEBS Open Bio. 2021 Feb;11(2):367-374. doi: 10.1002/2211-5463.13040. Epub 2021 Jan 1.

Abstract

The Golgi-localized, gamma-ear containing, ADP-ribosylation factor-binding proteins (GGAs 1, 2, and 3) are multidomain proteins that bind mannose 6-phosphate receptors (MPRs) at the Golgi and play a role, along with adaptor protein complex 1 (AP-1), in the sorting of newly synthesized lysosomal hydrolases to the endolysosomal system. However, the relative importance of the two types of coat proteins in this process is still unclear. Here, we report that inactivation of all three GGA genes in HeLa cells decreased the sorting efficiency of cathepsin D from 97% to 73% relative to wild-type, with marked redistribution of the cation-independent MPR from peripheral punctae to the trans-Golgi network. In comparison, GNPTAB-/- HeLa cells with complete inactivation of the mannose 6-phosphate pathway sorted only 20% of the cathepsin D. We conclude that the residual sorting of cathepsin D in the GGA triple-knockout cells is mediated by AP-1.

Keywords: AP-1; CI-MPR; GGA1; GGA2; GGA3; cathepsin D sorting.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Protein Complex 1 / metabolism*
  • Adaptor Proteins, Vesicular Transport / genetics
  • Adaptor Proteins, Vesicular Transport / metabolism*
  • Cathepsin D / metabolism*
  • Gene Knockout Techniques
  • HeLa Cells
  • Humans
  • Lysosomes / enzymology
  • Transferases (Other Substituted Phosphate Groups) / genetics
  • Transferases (Other Substituted Phosphate Groups) / metabolism
  • trans-Golgi Network / metabolism

Substances

  • Adaptor Protein Complex 1
  • Adaptor Proteins, Vesicular Transport
  • GGA adaptor proteins
  • GGA2 protein, human
  • Transferases (Other Substituted Phosphate Groups)
  • GNPTAB protein, human
  • CTSD protein, human
  • Cathepsin D