This continuing research is aimed at characterizing, with micro- and nanoscale resolution, the collective molecular events of cellular signaling that are initiated by plasma membrane receptors and are highly orchestrated in space and time. Focus remains primarily on the high affinity receptor for IgE, Fc?RI, on mast cells, which plays a pivotal role in the allergic immune response and serves as a valuable model system for receptor-mediated cellular signaling. The primary goal of these studies is to elucidate structural interactions of proteins and lipids occurring within the plasma membrane milieu that are altered by antigen crosslinking of IgE- Fc?RI and result in transmembrane triggering of intracellular signaling cascades, culminating in cellular responses to the stimulant. Proposed research will investigate mechanisms by which the actin cytoskeleton regulates these interactions at multiple levels, including membrane pinning and compartmentalization by the cortical meshwork that prevents spontaneous initiation of signaling and rearrangements associated with cell adherence to a substrate that adjust the level of response.
Specific Aim 1 will use two-color super resolution fluorescence microscopy to image and analyze dynamic interactions among signaling components in the plasma membrane that are initiated immediately after IgE-Fc?RI crosslinking, and regulation of these will be evaluated by selective perturbation to membrane and cytoskeleton. Structurally defined ligands will be employed to discern features of crosslinking that are critical for signal initiation, and these experimental results will be incorporated into computational models of signaling systems.
Specific Aim 2 will use versatile micro- patterned surfaces and fluorescence microscopy to investigate later-stage membrane interactions initiated by clustered IgE-Fc?RI leading to downstream signaling and cellular response events that are modulated by integrin engagement. Selective inhibitors and molecular tension sensors will be employed to probe participation of the actin cytoskeleton and integrins in imposing mechanical forces and regulating signaling networks, as related to consequent cellular responses in single cell assays.
Specific Aim 3 will translate biophysical insight and high-resolution approaches gained from detailed characterization of the IgE-Fc?RI model system to investigate plasma membrane interactions that participate in neurological cell activities and are disrupted in neurodegenerative diseases. The goal of these highly collaborative studies is to lay the groundwork and establish fruitful directions for significant biomedical impact. Initial experiments will evaluate cellular interactions of ?-synuclein that may occur in Parkinson's disease, cell surface clustering of neurotrophin receptor p75 related to signaling in neuronal plasticity, and lysosomal synapses that appear to be formed by microglia to hydrolyze A? fibrils associated with Alzheimer's disease.
The heterogeneous plasma membrane milieu of eukaryotic cells maintains a steady state of protein and lipid interactions that support basal cell function and, while serving as a selective barrier, is poised to respond appropriately to environmental stimuli. The primary goal of our continuing studies is molecular level elucidation of the structural interactions occurring within the dynamic plasma membrane that are altered by antigen crosslinking of IgE-Fc?RI to initiate intracellular signaling cascades in the allergic immune response. We will also engage in highly collaborative studies to translate insight and high-resolution approaches gained from detailed characterization of the IgE-Fc?RI model system to investigate plasma membrane interactions that participate in neurological cell activities and are disrupted in neurodegenerative diseases.
|Mitra, Eshan D; Whitehead, Samuel C; Holowka, David et al. (2018) Computation of a Theoretical Membrane Phase Diagram and the Role of Phase in Lipid-Raft-Mediated Protein Organization. J Phys Chem B 122:3500-3513|
|Holowka, David; Thanapuasuwan, Kankanit; Baird, Barbara (2018) Short chain ceramides disrupt immunoreceptor signaling by inhibiting segregation of Lo from Ld Plasma membrane components. Biol Open 7:|
|Holowka, David; Baird, Barbara (2017) Mechanisms of epidermal growth factor receptor signaling as characterized by patterned ligand activation and mutational analysis. Biochim Biophys Acta Biomembr 1859:1430-1435|
|Korzeniowski, Marek K; Wisniewski, Eva; Baird, Barbara et al. (2017) Molecular anatomy of the early events in STIM1 activation - oligomerization or conformational change? J Cell Sci 130:2821-2832|
|Wakefield, Devin L; Holowka, David; Baird, Barbara (2017) The Fc?RI Signaling Cascade and Integrin Trafficking Converge at Patterned Ligand Surfaces. Mol Biol Cell :|
|Holowka, David; Baird, Barbara (2016) Roles for lipid heterogeneity in immunoreceptor signaling. Biochim Biophys Acta 1861:830-836|
|Wilson, Joshua D; Shelby, Sarah A; Holowka, David et al. (2016) Rab11 Regulates the Mast Cell Exocytic Response. Traffic 17:1027-41|
|Shelby, Sarah A; Veatch, Sarah L; Holowka, David A et al. (2016) Functional nanoscale coupling of Lyn kinase with IgE-Fc?RI is restricted by the actin cytoskeleton in early antigen-stimulated signaling. Mol Biol Cell 27:3645-3658|
|Sun, Chao; Wakefield, Devin L; Han, Yimo et al. (2016) Graphene Oxide Nanosheets Stimulate Ruffling and Shedding of Mammalian Cell Plasma Membranes. Chem 1:273-286|