Associations Of Stim1 During Store-Operated Calcium Entry And Development Of A Novel Method For Multi-Biomolecule Patterning

To understand immune responses, such as asthma and allergies, we must first understand the inter- and intramolecular regulation of the signaling pathways responsible for these complex biological processes. Of particular importance in immune cell signaling is understanding Ca2+ mobilization and the pathway of store-operated Ca2+ entry (SOCE), wherein Ca2+ released from the endoplasmic reticulum (ER) stores leads to an influx of Ca2+ from the extracellular environment via Ca2+ release-activated Ca2+ (CRAC) channels. Activation of SOCE is accomplished by coupling of Ca2+ sensing stromal interaction molecule 1 (STIM1), an ER transmembrane protein, to Orai1 proteins located at the plasma membrane (PM). While numerous research efforts have focused on understanding the STIM1-Orai1 interactions required to elicit SOCE, much uncertainty remains about the associations that regulate STIM1 before and during SOCE. This dissertation provides new insights into the inter- and intramolecular interactions regulating STIM1, both at rest and following activation. Using immunoprecipitation (IP) assays, we provide evidence that STIM1 exists in multiple low-order oligomer states at rest, including a 110 kDa hetero-dimer with a 20-25 kDa unidentified protein (possibly a proteolytic fragment) and a 260 kDa homo-dimer complex. We further establish that non-covalent interactions are sufficient to maintain these oligomers in resting cells. However, following cell lysis, disulfide bonds form to stabilize the protein complexes. Following activation of STIM1 by thapsigargin, the presence and appearance of these oligomers is not detectably altered. Although we made multiple attempts to identify components of the 110 kDa and 260 kDa STIM1 complexes, we are unable to identify any components of the oligomeric species aside from STIM1. Following the discovery of the CRAC activation domain (CAD), which is the minimal region of STIM1 required to bind Orai1 and activate CRAC channels, much research has focused on understanding the exact interactions required to facilitate this process. Mutational analysis reveals that Cys-437 in the CAD region of STIM1 participates in the stabilization of the 110 kDa hetero-dimer protein complex. Using confocal microscopy and FRET analysis, we find that C437A mutant STIM1 translocates to the PM following store depletion and associates with Orai1 at a rate similar to that of wildtype STIM1. However, this same mutant STIM1 form exhibits a significant delay in SOCE as compared to wildtype, suggesting an important gating role for the Cys-437 residue in regulating SOCE. In a separate set of studies, we have collaborated in the development of a novel multibiomolecule patterning technique that utilizes fluorinated resist and developers, low-temperature and pressure conditions, and imprint lithography. We show that both the resist and developers are largely benign to biomolecules, including proteins and DNA, and are suitable for use in cell studies. We further demonstrate capacity of this method for multi-biomolecule patterning by fabricating multi-protein arrays and provide evidence that surface-immobilized biomolecules can undergo at least 10 cycles of lithographic processing with negligible deleterious effects. Importantly, the success of this patterning method demonstrates a new model for multibiomolecule patterning that avoids many of the problems associated with more traditional lithographic techniques