Articles by Mark A. Stamnes in JoVE
Informatic Analysis of Sequence Data from Batch Yeast 2-Hybrid Screens Venkatramanan Krishnamani1, Tabitha A. Peterson1, Robert C. Piper1, Mark A. Stamnes1 1Molecular Physiology and Biophysics, University of Iowa Deep sequencing of yeast populations selected for positive yeast 2-hybrid interactions potentially yields a wealth of information about interacting partner proteins. Here, we describe the operation of specific bioinformatics tools and customized updated software to analyze sequence data from such screens.
Other articles by Mark A. Stamnes on PubMed
ADP-ribosylation Factor and Phosphatidic Acid Levels in Golgi Membranes During Budding of Coatomer-coated Vesicles Proceedings of the National Academy of Sciences of the United States of America. | Pubmed ID: 9811859 The finding that ADP-ribosylation factor (ARF) can activate phospholipase D has led to debate as to whether ARF recruits coat proteins through direct binding or indirectly by catalytically increasing phosphatidic acid production. Here we test critical aspects of these hypotheses. We find that Golgi membrane phosphatidic acid levels do not rise-in fact they decline-during cell-free budding reactions. We confirm that the level of membrane-bound ARF can be substantially reduced without compromising coat assembly [Ktistakis, N. T., Brown, H. A., Waters, M. G., Sternweis, P. C. & Roth, M. G. (1996) J. Cell Biol. 134, 295-306], but find that under all conditions, ARF is present on the Golgi membrane in molar excess over bound coatomer. These results do not support the possibility that the activation of coat assembly by ARF is purely catalytic, and they are consistent with ARF forming direct interactions with coatomer. We suggest that ARF, like many other G proteins, is a multifunctional protein with roles in trafficking and phospholipid signaling.
Regulating the Actin Cytoskeleton During Vesicular Transport Current Opinion in Cell Biology. | Pubmed ID: 12383793 Although the actin cytoskeleton is widely believed to play an important role in intracellular protein transport, this role is poorly understood. Recently, progress has been made toward identifying specific actin-binding proteins and signaling molecules involved in regulating actin structures that function in the secretory pathway. Studies on coat protomer I (COPI)-mediated transport at the Golgi apparatus and on clathrin-mediated endocytosis have been particularly informative in identifying such mechanisms. Important similarities between actin regulation at the Golgi and at the plasma membrane have been uncovered. The studies reveal that ADP-ribosylation factor and vesicle coat proteins are able to act through the Rho-family GTP-binding proteins, Cdc42 and Rac, and several specific actin-binding proteins to direct actin assembly through the Arp2/3 complex. Efficient function of the secretory pathway is likely to require precise temporal regulation among transport-vesicle assembly, vesicle scission, and the targeting machinery. It is proposed that numerous actin regulatory mechanisms and the connections between actin signaling and vesicle-coat formation are employed to provide such temporal regulation.
CLN3 Deficient Cells Display Defects in the ARF1-Cdc42 Pathway and Actin-dependent Events PloS One. | Pubmed ID: 24792215 Juvenile Batten disease (juvenile neuronal ceroid lipofuscinosis, JNCL) is a devastating neurodegenerative disease caused by mutations in CLN3, a protein of undefined function. Cell lines derived from patients or mice with CLN3 deficiency have impairments in actin-regulated processes such as endocytosis, autophagy, vesicular trafficking, and cell migration. Here we demonstrate the small GTPase Cdc42 is misregulated in the absence of CLN3, and thus may be a common link to multiple cellular defects. We discover that active Cdc42 (Cdc42-GTP) is elevated in endothelial cells from CLN3 deficient mouse brain, and correlates with enhanced PAK-1 phosphorylation, LIMK membrane recruitment, and altered actin-driven events. We also demonstrate dramatically reduced plasma membrane recruitment of the Cdc42 GTPase activating protein, ARHGAP21. In line with this, GTP-loaded ARF1, an effector of ARHGAP21 recruitment, is depressed. Together these data implicate misregulated ARF1-Cdc42 signaling as a central defect in JNCL cells, which in-turn impairs various cell functions. Furthermore our findings support concerted action of ARF1, ARHGAP21, and Cdc42 to regulate fluid phase endocytosis in mammalian cells. The ARF1-Cdc42 pathway presents a promising new avenue for JNCL therapeutic development.