PMID- 8662952
OWN - NLM
STAT- MEDLINE
DCOM- 19960820
LR  - 20210210
IS  - 0021-9258 (Print)
IS  - 0021-9258 (Linking)
VI  - 271
IP  - 24
DP  - 1996 Jun 14
TI  - Inhibition of cellular processing of surfactant protein C by drugs affecting 
      intracellular pH gradients.
PG  - 14361-70
AB  - Surfactant protein C (SP-C) is a hydrophobic protein synthesized and secreted 
      exclusively by alveolar type II cells through proteolysis of a 21-kDa propeptide 
      (SP-C21) to produce the 3.7-kDa surface active form. Previous studies from this 
      laboratory have demonstrated that early processing of proSP-C involves extensive 
      intracellular proteolysis of the COOH terminus of proSP-C21 in subcellular 
      compartments, which include the acidic type II cell-specific subcellular 
      organelle, the lamellar body. (Beers, M. F., Kim, C. Y., Dodia, C., and Fisher, 
      A. B.(1994) J. Biol. Chem. 269, 20318-20328). The role of intracellular pH 
      gradients in SP-C processing was studied in freshly isolated rat type II cells. 
      Using vital fluorescence microscopy, the pH indicator acridine orange (AO) 
      identified intense fluorescence staining of acidic cytoplasmic vesicles within 
      fresh type II cells. The AO vesicular staining pattern was similar in cells 
      labeled with the lamellar body marker phosphine 3R and the phospholipid dye nile 
      red. AO fluorescence was quenched by the addition of a membrane-permeable weak 
      base, methylamine. Immunoprecipitation of cell lysates with anti-proSP-C antisera 
      following pulse-chase labeling (0-2 h) with 35S-Translabel demonstrated rapid 
      synthesis of 35S-proSP-C21 with a time-dependent appearance of 16- and 6-kDa 
      intermediates (SP-C16 and SP-C6). Tricine polyacrylamide gel electrophoresis 
      analysis of organic extracts of cell lysates showed time-dependent appearance of 
      mature SP-C3.7. The addition of 5 mM methylamine significantly blocked the 
      post-translational processing of proSP-C resulting in disruption of normal 
      precursor-product relationships and inhibition of SP-C3.7 formation. 
      Methylamine-treated cells exhibited slow accumulation of SP-C16 and SP-C6, a 
      persistence of SP-C21, and an absence of SP-C3.7 for the duration of the chase 
      period. The lysosomotropic agent chloroquine, the proton ionophore monensin, and 
      bafilomycin A1, a specific vacuolar H+-ATPase inhibitor, each caused inhibition 
      of proSP-C processing in a similar manner. These results demonstrate that normal 
      post-translational proteolysis of proSP-C occurs in acidic intracellular 
      compartments, which include the lamellar body, and that complete processing to 
      SP-C3.7 is dependent upon maintenance of transmembrane pH gradients by a vacuolar 
      H+-ATPase.
FAU - Beers, M F
AU  - Beers MF
AD  - Institute for Environmental Medicine, University of Pennsylvania School of 
      Medicine, Philadelphia, Pennsylvania 19104-6068, USA.
LA  - eng
GR  - HL-02869/HL/NHLBI NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - J Biol Chem
JT  - The Journal of biological chemistry
JID - 2985121R
RN  - 0 (Anti-Bacterial Agents)
RN  - 0 (Antibodies)
RN  - 0 (Enzyme Inhibitors)
RN  - 0 (Epitopes)
RN  - 0 (Ionophores)
RN  - 0 (Macrolides)
RN  - 0 (Methylamines)
RN  - 0 (Protein Precursors)
RN  - 0 (Proteolipids)
RN  - 0 (Pulmonary Surfactants)
RN  - 0 (Sulfur Radioisotopes)
RN  - 886U3H6UFF (Chloroquine)
RN  - 88899-55-2 (bafilomycin A1)
RN  - 906O0YJ6ZP (Monensin)
RN  - BSF23SJ79E (methylamine)
SB  - IM
MH  - Animals
MH  - Anti-Bacterial Agents/pharmacology
MH  - Antibodies
MH  - Cells, Cultured
MH  - Chloroquine/pharmacology
MH  - Enzyme Inhibitors/pharmacology
MH  - Epitopes
MH  - Hydrogen-Ion Concentration
MH  - Ionophores/pharmacology
MH  - Kinetics
MH  - Lung/cytology/*metabolism
MH  - *Macrolides
MH  - Methylamines/*pharmacology
MH  - Models, Biological
MH  - Monensin/*pharmacology
MH  - Protein Precursors/isolation & purification/metabolism
MH  - Protein Processing, Post-Translational/*drug effects
MH  - Proteolipids/*biosynthesis/isolation & purification
MH  - Pulmonary Surfactants/*biosynthesis/isolation & purification
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - Subcellular Fractions/drug effects/metabolism
MH  - Sulfur Radioisotopes
MH  - Time Factors
MH  - Vacuoles/drug effects/metabolism
EDAT- 1996/06/14 00:00
MHDA- 1996/06/14 00:01
CRDT- 1996/06/14 00:00
PHST- 1996/06/14 00:00 [pubmed]
PHST- 1996/06/14 00:01 [medline]
PHST- 1996/06/14 00:00 [entrez]
AID - S0021-9258(18)46808-1 [pii]
AID - 10.1074/jbc.271.24.14361 [doi]
PST - ppublish
SO  - J Biol Chem. 1996 Jun 14;271(24):14361-70. doi: 10.1074/jbc.271.24.14361.