Barbara BernsteinResearch Professor
Office: Chemistry C326B
Phone: 970-491-6347
Research Title: Cofilin-regulated Actin in Neuronal Function

How cofilin regulation contributes to neuronal health

The actin cytoskeleton has extensive control over numerous aspects of cell behavior ranging from organelle translocation and plasma membrane ionic flux to gene expression. Often these processes require precise spatio-temporal coordination of actin filament assembly and disassembly which then can feed back to modify positively or negatively these dynamics. Our work has focused on understanding how the actin cytoskeleton affects both the normal and abnormal functioning of one cell type in particular, neurons. The research has had an emphasis on cofilin, an essential, critical regulator of actin dynamics with the additional capability of maintaining cellular homeostasis.

We have shown that depolarization, which stimulates neurotransmitter release, also drives oscillations in filamentous actin levels and that such oscillations can consume up to 50% of the ATP used by cultured neurons. In probing mechanisms behind these oscillations, we have concentrated on cofilin and have learned the following: 1) Cofilin’s actin depolymerizing and severing capabilities are inhibited by tropomyosin binding to filaments, and 2) In cells cofilin is modulated by pH shifts as small as those following growth factor stimulation or neuronal excitation.

The excitotoxic levels of glutamate, following brain injury or ischemia, elevate the cellular oxidation state and produce cofilin oligomerization through disulfide bonding. This oxidation-induced cofilin oligomerization underlies the formation of rod-shaped actin/cofilin inclusions (“rods”) in axons and dendrites. Rods are initially reversible and beneficial in that they slow ATP decline and mitochondrial membrane potential decline. If they persist rods can be either beneficial or detrimental. They reduce the amount of cofilin available for triggering apoptosis which occurs with more intense oxidation. However, rods also block axonal transport and cause complete degeneration of the neurite distal to their location. To learn more about redox processes responsible for rod generation, rod formation itself, and the likely link between rods and neurodegenerative diseases, such as, Alzheimer’s disease, we have used a range of molecular biology techniques and light microscopy (wide field, confocal, and TIRF).

Reference List

Mi J, Shaw AE, Pak CW, Walsh KP, Minamide LS, Bernstein BW, Kuhn TB, Bamburg JR (2013) A genetically encoded reporter for real-time imaging of cofilin-actin rods in living neurons. PLoS One 8: e83609.

Bernstein BW, Shaw AE, Minamide LS, Pak CW, Bamburg JR (2012) Incorporation of cofilin into rods depends on disulfide intermolecular bonds: implications for actin regulation and neurodegenerative disease. J Neurosci 32: 6670-6681.

Bamburg JR, Bernstein BW (2010) Roles of ADF/cofilin in actin polymerization and beyond. F1000 Biol Rep 2: 62.

Bernstein BW, Bamburg JR (2010) Neuronal guidance: a redox signal involving Mical. Curr Biol 20: R360-R362.

Bernstein BW, Bamburg JR (2010) ADF/cofilin: a functional node in cell biology. Trends Cell Biol 20: 187-195.

Bamburg JR, Bernstein BW, Davis RC, Flynn KC, Goldsbury C, Jensen JR, Maloney MT, Marsden IT, Minamide LS, Pak CW, Shaw AE, Whiteman I, Wiggan O (2010) ADF/Cofilin-actin rods in neurodegenerative diseases. Curr Alzheimer Res 7: 241-250.

Bamburg JR, Bernstein BW (2008) ADF/cofilin. Curr Biol 18: R273-R275.

Bernstein BW, Chen H, Boyle JA, Bamburg JR (2006) Formation of actin-ADF/cofilin rods transiently retards decline of mitochondrial potential and ATP in stressed neurons. Am J Physiol Cell Physiol 291: C828-C839.

Wiggan O, Bernstein BW, Bamburg JR (2005) A phosphatase for cofilin to be HAD. Nat Cell Biol 7: 8-9.

Chen H, Bernstein BW, Sneider JM, Boyle JA, Minamide LS, Bamburg JR (2004) In vitro activity differences between proteins of the ADF/cofilin family define two distinct subgroups. Biochemistry 43: 7127-7142.

Bernstein BW, Bamburg JR (2004) A proposed mechanism for cell polarization with no external cues. Cell Motil Cytoskeleton 58: 96-103.

Minamide LS, Shaw AE, Sarmiere PD, Wiggan O, Maloney MT, Bernstein BW, Sneider JM, Gonzalez JA, Bamburg JR (2003) Production and use of replication-deficient adenovirus for transgene expression in neurons. Methods Cell Biol 71: 387-416.

Bernstein BW (2003) Dissection and culturing of chick ciliary ganglion neurons: a system well suited to synaptic study. Methods Cell Biol 71: 37-50.

Bernstein BW, Bamburg JR (2003) Actin-ATP hydrolysis is a major energy drain for neurons. J Neurosci 23: 1-6.

Jha MN, Bamburg JR, Bernstein BW, Bedford JS (2002) Caffeine eliminates gamma-ray-induced G2-phase delay in human tumor cells but not in normal cells. Radiat Res 157: 26-31.

Bernstein BW, Painter WB, Chen H, Minamide LS, Abe H, Bamburg JR (2000) Intracellular pH modulation of ADF/cofilin proteins. Cell Motil Cytoskeleton 47: 319-336.

Kuhn TB, Meberg PJ, Brown MD, Bernstein BW, Minamide LS, Jensen JR, Okada K, Soda EA, Bamburg JR (2000) Regulating actin dynamics in neuronal growth cones by ADF/cofilin and rho family GTPases. J Neurobiol 44: 126-144.

Chen H, Bernstein BW, Bamburg JR (2000) Regulating actin-filament dynamics in vivo. Trends Biochem Sci 25: 19-23.

Bernstein BW, DeWit M, Bamburg JR (1998) Actin disassembles reversibly during electrically induced recycling of synaptic vesicles in cultured neurons. Brain Res Mol Brain Res 53: 236-251.

Bernstein BW, Bamburg JR (1992) Actin in emerging neurites is recruited from a monomer pool. Mol Neurobiol 6: 95-106.

Bernstein BW, Bamburg JR (1989) Cycling of actin assembly in synaptosomes and neurotransmitter release. Neuron 3: 257-265.

Giuliano KA, Khatib FA, Hayden SM, Daoud EW, Adams ME, Amorese DA, Bernstein BW, Bamburg JR (1988) Properties of purified actin depolymerizing factor from chick brain. Biochemistry 27: 8931-8938.

Bernstein BW, Bamburg JR (1987) Depolarization of brain synaptosomes activates opposing factors involved in regulating levels of cytoskeletal actin. Neurochem Res 12: 929-935.

Bernstein BW, Bamburg JR (1985) Reorganization of actin in depolarized synaptosomes. J Neurosci 5: 2565-2569.

Harris HE, Bamburg JR, Bernstein BW, Weeds AG (1982) The depolymerization of actin by specific proteins from plasma and brain: a quantitative assay. Anal Biochem 119: 102-114.

Bernstein BW, Bamburg JR (1982) Tropomyosin binding to F-actin protects the F-actin from disassembly by brain actin-depolymerizing factor (ADF). Cell Motil 2: 1-8.

Heacock CS, Bernstein BW, Duhaiman AS, Amorese DA, Bamburg JR (1982) In vitro labeling of proteins by reductive methylation: application to proteins involved in supramolecular structures. J Cell Biochem 19: 77-91.

Bernstein BW, Maloney MT, Pak C, and Bamburg JR (2011) The actin cytoskeleton and nervous system disease. In Neurobiology of Actin, edited by G Gallo and L Lanier, Springer Press, NY.

Bamburg JR and Bernstein BW (1991) Actin and actin-binding proteins in neurons. In The Neuronal Cytoskeleton, edited by RD Burgoyne, Wiley-Liss Publishers, NY.

Malhotra SK and Bernstein BW (1967) Unidentified bodies in certain nerve cells of Aplysia. In Invertebrate Nervous Systems, edited by CAG Wiersma, University of Chicago Press, IL.