Graydon B. Gonsalvez, PhD

Education & Post Doctoral Training

Education

94-98 BA Carthage College, Kenosha, WI

98-04 PhD. Medical College of Wisconsin, Milwaukee, WI

Post Doctoral Training

04-07 Case Western Reserve University, Cleveland, OH

07-09 University of North Carolina, Chapel Hill, NC

Current Funding

The Gonsalvez lab is currently funded by an R01 grant from the National Institutes of General Medical Sciences (2013-2018). Past funding include a grant from the American Cancer Society and an intramural grant from Augusta University.

Research Goals: Most eukaryotic cells are highly polarized and require polarity for proper function. Consequently, a contributing factor to a wide spectrum of human diseases is defective cell polarity. Our lab examines the mechanisms by which cells establish and maintain polarity.

How do cells establish polarity? The key to establishing polarity is to sort certain proteins to specific sites within the cell. For instance, the apical surface of an epithelial cell contains a different set of proteins than those found at the basolateral surface. Similarly, the proteins found within the axon of a neuron are often different from those founds at the tips of dendrites. The cell accomplishes this task of protein sorting using several mechanisms.

mRNA localization. Many cell types in the human body establish polarity via a process known as mRNA localization. This process enables the cell to restrict the synthesis of proteins to a particular region within the cell. The model organism that we use for these studies is Drosophila melanogaster (fruit fly). In particular, our lab examines the localization of oskar mRNA in Drosophila oocytes. oskar mRNA is an ideal candidate for investigation because the factors involved in its localization also function to localize mRNAs in mammalian cells. However, the Drosophila model provides us with the unique opportunity to study the process of mRNA localization in the context of the whole organism, rather than using isolated cells in culture. In addition, the wide array of genetic and molecular tools available for use with Drosophila will facilitate deeper and more rapid discovery. We have recently demonstrated that localization of oskar mRNA requires the concerted activities of two microtubule motor proteins, Kinesin and Dynein. An important next question is to determine the mechanism by which these motors associate with oskar mRNA.

The top left panel in the above figure shows a control egg chamber. The motor, Dynein, as well as oskar mRNA are localized at the posterior pole. The bottom panel represents an egg chamber in which Dynein has been depleted. This results in the delocalization of oskar mRNA.
The top middle panel of this figure illustrates the large endocytic intermediates that are observed when Dynein function is compromised (large circles). The bottom panel show electron microscopy images from control (left) and Dynein inhibited (right) egg chambers.
The top right panel of this figure shows a control Drosophila S2 cells that is expressing GFP. In the middle panel, the cell is over-expressing GFP-Sh3px1. This cell has formed long tubules. The bottom panel shows a cell over-expressing GFP-Sh3px1. This cell has formed long protrusions.

Endocytosis. Endocytosis is the mechanism by which cargoes are internalized and sorted within the cell. In addition to mRNA localization, endocytic trafficking also contributes to the establishment of cell polarity. Our lab has recently shown that the Dynein motor complex performs an essential function in endocytic maturation. When Dynein is inhibited, internalized cargo is trapped in enlarged endocytic vesicles (larges circles in the top panel). Our current efforts are focused on determining the precise mechanism by which Dynein functions in the endocytic pathway.

In order for cargo to be trafficked through the endocytic pathway, the membrane on endocytic vesicles has to become curved. This is a thermodynamically unfavorable process. Protein containing a domain known as a BAR domain are known to aid in this process. BAR domain proteins generate either membrane tubules or protrusions when over-expressed in cells. Our lab is currently studying the functions of a protein called Sh3px1. This protein contains a unique kind of BAR domain. When Sh3px1 is over-expressed in cells, it dramatically alters cell morphology. Some cells form long tubules, whereas other cells form long membrane protrusions. We are currently exploring the role of Sh3xp1 in development and tissue morphogenesis.

Long term goals: Defects in cell polarity are associated with several diseases including cancer, polycystic kidney disease and Charcot-Marie-Tooth disorder. The long-term goal of our research is to design better therapies to treat these debilitating diseases by determining how healthy cells establish polarity, and by understanding the way in which defective molecular pathways contribute to the disease state.

Approaches: We use a variety of tools such as genetics, cell biology and biochemistry to test our hypotheses. Numerous molecular techniques such as RT-PCR, western blotting, immunoprecipitation and in situ hybridization are routinely used. Studies are performed using Drosophila, Drosophila cell lines and mammalian cell lines.

Current Members of the lab

Phylicia Allen

Graduate Student

Jessica Pride

Graduate Student

Hannah Neiswender

Research Associate

Rajalakshmi Veeranan Karmegam

Research Associate

Publications

Activation of receptor-independent fluid-phase pinocytosis promotes foamy monocyte formation in atherosclerotic mice.
Ahn W, Burnett FN, Wojnar-Lason K, Doja J, Sreekumar A, Ghoshal P, Singla B, Gonsalvez G, Harris RA, Wang X, Miano JM, Csányi G.Redox Biol. 2024 Dec;78:103423. doi: 10.1016/j.redox.2024.103423. Epub 2024 Nov 6.PMID: 39615283

Endothelial ENaC-α Restrains Oxidative Stress in Lung Capillaries in Murine Pneumococcal Pneumonia-associated Acute Lung Injury.

Romero MJ, Yue Q, Ahn WM, Hamacher J, Zaidi Y, Haigh S, Sridhar S, Gonzales J, Hudel M, Huo Y, Verin AD, Pace BS, Stansfield BK, Maishan M, Neptune ER, Enkhbaatar P, Su Y, Chakraborty T, Gonsalvez G, Hummler E, Davis WB, Bogdanov VY, Fulton DJR, Csanyi G, Matthay MA, Eaton DC, Lucas R.Am J Respir Cell Mol Biol. 2024 Oct 15. doi: 10.1165/rcmb.2023-0440OC. Online ahead of print.PMID: 39405473

Defining the ligand-dependent proximatome of the sigma 1 receptor.

Zhao J, Veeranan-Karmegam R, Baker FC, Mysona BA, Bagchi P, Liu Y, Smith SB, Gonsalvez GB, Bollinger KE.Front Cell Dev Biol. 2023 Jun 7;11:1045759. doi: 10.3389/fcell.2023.1045759. eCollection 2023.PMID: 37351276

dTtc1, a conserved tetratricopeptide repeat protein, is required for maturation of Drosophila egg chambers via its role in stabilizing electron transport chain components.

Neiswender H, Baker FC, Veeranan-Karmegam R, Allen P, Gonsalvez GB.Front Cell Dev Biol. 2023 Jun 2;11:1148773. doi: 10.3389/fcell.2023.1148773. eCollection 2023.PMID: 37333987

Sigma 1 Receptor Contributes to Astrocyte-Mediated Retinal Ganglion Cell Protection.
Zhao J, Gonsalvez GB, Mysona BA, Smith SB, Bollinger KE.Invest Ophthalmol Vis Sci. 2022 Feb 1;63(2):1. doi: 10.1167/iovs.63.2.1.PMID: 35103752

PubMed Publications Pure Research

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