Identification of ras and ras-related Low-molecular-mass GTP-binding Proteins Associated with Rat Lung Lamellar Bodies
- 1 March 1992
- journal article
- Published by American Thoracic Society in American Journal of Respiratory Cell and Molecular Biology
- Vol. 6 (3) , 253-259
- https://doi.org/10.1165/ajrcmb/6.3.253
Abstract
Recent evidence from genetic experiments in yeast and from studies using guanosine triphosphate (GTP) analogues in mammalian cells suggests a key role for low-molecular-mass GTP-binding proteins (LMM-GBPs) (Mr 19 to 28 kD) in processes of intracellular vesicular sorting and secretion. Assembly and exocytosis of the lamellar body (LB), the secretory organelle of the pulmonary alveolar type 2 pneumocyte, may be regulated by LMM-GBPs. We used [alpha-32P]GTP binding to Western blotted proteins, ultraviolet crosslinking of [alpha-32P]GTP to membrane proteins, immunoblotting with specific antisera, and botulinum exoenzyme C3-catalyzed ADP ribosylation to detect LMM-GBPs in LB. With the first two techniques, we have identified six LMM-GBPs of approximately 27, 25.5, 24.5, 23, 22, and 21 kD that are enriched in a highly purified LB fraction compared with type 2 pneumocyte homogenate, crude membranes, and cytosol. Further characterization of the LB LMM-GBPs by immunoblotting revealed that ras p21 is greatly enriched in the LB fraction compared with other type 2 pneumocyte fractions. In addition, botulinum exoenzyme C3 catalyzed the ADP ribosylation of 20- to 21-kD proteins that were similarly enriched in the LB fraction. In contrast, a monospecific antibody to ADP-ribosylation factor reacted with a 19-kD protein only in the type 2 pneumocyte homogenate and cytosol fractions. Monospecific antibodies to yeast Sec4 protein and to rab 3A did not react with any type 2 pneumocyte proteins. The LMM-GBPs specifically associated with LB may participate in intracellular events required for surfactant packaging and secretion.Keywords
This publication has 36 references indexed in Scilit:
- Secretory Vesicle-Associated Proteins and Their Role in ExocytosisAnnual Review of Physiology, 1990
- Identification and localization of low-molecular-mass GTP-binding proteins associated with synaptic vesicles and other membranesBiochimica et Biophysica Acta (BBA) - Biomembranes, 1990
- Detection of low molecular mass GTP‐binding proteins in chromaffin granules and other subcellular fractions of chromaffin cellsFEBS Letters, 1989
- Multiple small molecular weight gtp-binding proteins in bovine brain cytosol purification and characterization of a 24KDa proteinBiochemical and Biophysical Research Communications, 1988
- A GTP-binding protein required for secretion rapidly associates with secretory vesicles and the plasma membrane in yeastCell, 1988
- Involvement of GTP-binding “G” proteins in transport through the Golgi stackCell, 1987
- Isolation of lamellar bodies from rat granular pneumocytes in primary cultureBiochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1983
- Localization of the src gene product of the Harvey strain of MSV to plasma membrane of transformed cells by electron microscopic immunocytochemistryCell, 1980
- Pulmonary Alveolar Type II Cells Isolated from RatsJournal of Clinical Investigation, 1979
- Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4Nature, 1970