Role of phospholipase A<sub>2</sub>-dependent membrane tubules and platelet-activating factor acetyl-hydrolase isoform IB alpha-1 and alpha-2 subunits in membrane trafficking pathways

2005 2005

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Abstract (summary)

Proper functioning of the secretory and endocytic pathways is critical to the structural and functional organization of eukaryotic cells. Transport of material within these pathways maintains a necessary balance of membrane and protein. Vesicle-mediated transport has been studied extensively. However, the molecular mechanisms of membrane tubule-mediated transport are not well understood. Evidence suggests that cytoplasmic calcium-independent phospholipase A2 (PLA2) activity is involved in the direct formation of membrane tubules from the Golgi complex, trans Golgi network (TGN), and endosomes. The focus of this work is to examine the role of PLA 2 enzymes in various membrane trafficking pathways and to demonstrate a role for platelet-activating factor acetyl-hydrolase isoform Ib (PAF-AH Ib) α1 and α2 subunits in tubule formation.

Previous studies have shown that export of transferrin and transferrin receptor from early sorting endosomes (ESEs) and the endocytic recycling compartment (ERC) is mediated in part by PLA2-dependent membrane tubules. Studies here show that tubules are a general feature of intracellular trafficking pathways. I show that PLA2 activity is likely involved in trafficking pathways from ESEs to late endosomes (LEs), from LEs to lysosomes, and from the ERC to the TGN.

I have also found a novel role for the Ca2+-independent PLA2 PAF-AH Ib α1 and α2 subunits. These proteins are found in bovine brain cytosol and are capable of inducing tubulation of Golgi membranes in vitro. In addition, over-expression of α1 or α2 disrupts the normal localization of proteins found in the Golgi complex, TGN, late endosomes, and lysosomes. Furthermore, the normal trafficking of cargo through the recycling and degradative endocytic pathways is altered by over-expression of α1.

These results are consistent with the model that a cytoplasmic Ca 2+-independent PLA2 is involved in tubulation of Golgi and endosomal membranes, and that tubules play a general role in the trafficking of cargo through the secretory and endocytic pathways. These studies also suggest a novel role for PAF-AH Ib in membrane trafficking. Understanding the exact role of the PAF-AH Ib subunits in membrane tubulation and how the actions of these subunits are regulated will help to elucidate the mechanisms underlying intracellular trafficking pathways.

Indexing (details)

Cellular biology;
Molecular biology
0379: Cellular biology
0487: Biochemistry
0307: Molecular biology
Identifier / keyword
Pure sciences; Biological sciences; Acetyl-hydrolase; Membrane trafficking; Membrane tubules; Phospholipase A2; Platelet-activating factor
Role of phospholipase A<sub>2</sub>-dependent membrane tubules and platelet-activating factor acetyl-hydrolase isoform IB alpha-1 and alpha-2 subunits in membrane trafficking pathways
Doody, Anne Marie
Number of pages
Publication year
Degree date
School code
DAI-B 66/01, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
0496962027, 9780496962020
Brown, William
Cornell University
University location
United States -- New York
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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