Inhibition of membrane tubule formation and trafficking by isotetrandrine, an antagonist of G-protein-regulated phospholipase A2 enzymes.
Previous studies have established a role for cytoplasmic phospholipase A(2) (PLA(2)) activity in tubule-mediated retrograde trafficking between the Golgi complex and the endoplasmic reticulum (ER). However, little else is known about how membrane tubule formation is regulated. This study demonstrates that isotetrandrine (ITD), a biscoclaurine alkaloid known to inhibit PLA(2) enzyme activation by heterotrimeric G-proteins, effectively prevented brefeldin A (BFA)-induced tubule formation from the Golgi complex and retrograde trafficking to the ER. In addition, ITD inhibited BFA-stimulated tubule formation from the trans-Golgi network and endosomes. ITD inhibition of the BFA response was potent (IC(50) approximately 10-20 microM) and rapid (complete inhibition with a 10-15-min preincubation). ITD also inhibited normal retrograde trafficking as revealed by the formation of nocodazole-induced Golgi mini-stacks at ER exit sites. Treatment of cells with ITD alone caused the normally interconnected Golgi ribbons to become fragmented and dilated, but cisternae were still stacked and located in a juxtanuclear position. These results suggest that a G-protein-binding PLA(2) enzyme plays a pivotal role in tubule mediated trafficking between the Golgi and the ER, the maintenance of the interconnected ribbons of Golgi stacks, and tubule formation from endosomes.
Chan
Diane
D
Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 18483, USA.
Strang
Marian
M
Judson
Bret
B
Brown
William J
WJ
D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D044182:Benzylisoquinolines / Q000494:pharmacology*; D001692:Biological Transport; D020126:Brefeldin A / Q000737:chemistry / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D015739:Nocodazole / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D013997:Time Factors
D000470:Alkaloids; D000970:Antineoplastic Agents; D044182:Benzylisoquinolines; D002121:Calcium Channel Blockers; D011500:Protein Synthesis Inhibitors; D020126:Brefeldin A; C009438:tetrandrine; D010741:Phospholipases A; D054467:Phospholipases A2; D019204:GTP-Binding Proteins; D015739:Nocodazole