PMID- 7511608
OWN - NLM
STAT- MEDLINE
DCOM- 19940505
LR  - 20210210
IS  - 0021-9258 (Print)
IS  - 0021-9258 (Linking)
VI  - 269
IP  - 14
DP  - 1994 Apr 8
TI  - Retention and degradation of proteins containing an uncleaved 
      glycosylphosphatidylinositol signal.
PG  - 10830-7
AB  - Glycosylphosphatidylinositol (GPI) membrane anchor attachment is directed by a 
      COOH-terminal signal that is proteolytically removed and replaced with a 
      preformed GPI anchor in a coupled reaction. Failure to complete proteolytic 
      cleavage and anchor addition results in the retention of an uncleaved precursor 
      in a post-endoplasmic reticulum (ER) compartment. In this report, we address 
      three issues: (i) the exact position of the transport block, (ii) the subsequent 
      fate of the retained molecules, i.e. where are they degraded, and (iii) the 
      mechanism whereby these proteins are selected for retention. Using decay 
      accelerating factor (DAF), we provide evidence that failure to cleave the GPI 
      signal totally prevents O-glycosylation, suggesting that the uncleaved 
      polypeptides are not transported into the cis-Golgi complex. This implies that 
      transport is blocked at the boundary between the ER-Golgi intermediate 
      compartment and the Golgi stacks. The degradation of an intracellularly retained 
      human growth hormone (hGH)-DAF fusion protein containing a nonfunctional GPI 
      signal shows some features of ER degradation, i.e. the degradation is insensitive 
      to leupeptin, chloroquine, and ammonium chloride, and is inhibited at 16 degrees 
      C or after ATP depletion. However, morphological evidence points to a pathway 
      resembling autophagy. To reconcile these observations, we suggest either that 
      hGHDAF is degraded by two distinct pathways (ER degradation and autophagy) or 
      that ER degradation takes place in an ER-associated vesicular compartment in a 
      process resembling autophagy. Using as probes a soluble hGH receptor and an 
      antibody recognizing only native hGH, we show that a significant fraction of the 
      retained protein is correctly folded, ruling out general misfolding as the basis 
      for retention. We also show that hGHDAF fusion proteins are present in high 
      molecular weight, disulfide-linked aggregates in COS cells. We suggest a model 
      for retention in which the uncleaved GPI signal drives the formation of large 
      micelle-like aggregates that cannot be secreted.
FAU - Field, M C
AU  - Field MC
AD  - Department of Neurobiology, Genentech Inc., South San Francisco, California 
      94080.
FAU - Moran, P
AU  - Moran P
FAU - Li, W
AU  - Li W
FAU - Keller, G A
AU  - Keller GA
FAU - Caras, I W
AU  - Caras IW
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Biol Chem
JT  - The Journal of biological chemistry
JID - 2985121R
RN  - 0 (Antigens, CD)
RN  - 0 (CD55 Antigens)
RN  - 0 (Glycosylphosphatidylinositols)
RN  - 0 (Membrane Glycoproteins)
RN  - 0 (Recombinant Fusion Proteins)
RN  - 9002-72-6 (Growth Hormone)
RN  - EC 3.4.23.5 (Cathepsin D)
SB  - IM
MH  - Amino Acid Sequence
MH  - Animals
MH  - Antigens, CD/*metabolism
MH  - CD55 Antigens
MH  - CHO Cells
MH  - Cathepsin D/metabolism
MH  - Cell Line
MH  - Cricetinae
MH  - Glycosylation
MH  - Glycosylphosphatidylinositols/*metabolism
MH  - Growth Hormone/*metabolism
MH  - Humans
MH  - Lysosomes/metabolism
MH  - Membrane Glycoproteins/*metabolism
MH  - Microscopy, Immunoelectron
MH  - Molecular Sequence Data
MH  - Protein Folding
MH  - Recombinant Fusion Proteins/metabolism
EDAT- 1994/04/08 00:00
MHDA- 1994/04/08 00:01
CRDT- 1994/04/08 00:00
PHST- 1994/04/08 00:00 [pubmed]
PHST- 1994/04/08 00:01 [medline]
PHST- 1994/04/08 00:00 [entrez]
AID - S0021-9258(17)34134-0 [pii]
PST - ppublish
SO  - J Biol Chem. 1994 Apr 8;269(14):10830-7.