(M) pcbi.1007708.s002.m (13K) GUID:?838A4E45-2615-4C5E-A63A-4924B9BEE74C S1 Fig: Time courses of all model species for Fig 2A, 10% steepness and = 0.1. activation and the difference in receptor activation across its length were calculated. Cells with receptor activation says above the curve engaged Bepridil hydrochloride in chemotaxis, whereas those with says below the curve engaged in random migration only.(PDF) pcbi.1007708.s008.pdf (35K) GUID:?B20D0982-D380-44C7-874E-D4AD19521883 S1 Movie: Animation of the simulation depicted in Fig 7A. (AVI) pcbi.1007708.s009.avi (11M) GUID:?0A43175D-0CE0-45A0-B11A-4A15E041B657 Attachment: Submitted filename: and S1 Text). The first, PFL 1, considers the modulation of PLC recruitment by phosphatidic acid Rabbit Polyclonal to LAT (PA), the lipid produced by phosphorylation of DAG by DAG kinases. Using a detergent-phospholipid mixed micelle assay system, it was shown that inclusion of PA enhanced PIP2 hydrolysis catalyzed by either unphosphorylated or tyrosine-phosphorylated PLC1, by reducing the apparent for the reaction . The details of how PA affects PLC activity are not completely comprehended, but the reduction of the apparent is usually consistent with PA-mediated stabilization of PLC1 association with the membrane, akin to the effect of the non-catalytic conversation of PLC with PIP2 . Therefore, we modeled the effect of Bepridil hydrochloride PA as an increased Bepridil hydrochloride lifetime of the receptor-PLC1 complex at the membrane (Fig 1A). Open in a separate windows Fig 1 Model of the PLC/PKC network including phosphatidic acid (PA).(A) Model schematic depicting the interactions and reactions among signaling proteins and plasma membrane lipids. Dashed lines ending in a packed circle indicate that this species enhances the associated process. The reactions and interactions shown in reddish are associated with the generation and influence of PA in positive feedback loops (PFLs) labeled (1) and (2). (B) Base model geometry and orientation of the receptor occupancy gradient, which is usually linear in the direction of the cells long axis, (relative midpoint density) and (relative steepness, expressed here as a percentage difference across the cell). PFL 2 considers the effect of active PKC on the activity of phospholipase D1 (PLD1), Bepridil hydrochloride which produces PA by hydrolyzing the abundant lipid, phosphatidylcholine [19,21]. In murine fibroblasts stimulated with phorbol ester, PKC interacts with PLD1 and increases the rate of phosphatidylcholine hydrolysis. PA produced by this reaction can be dephosphorylated to yield DAG, and thus PFL 2 exerts an influence on PLC/PKC signaling impartial of PFL 1. We model the influence of PLD as a distinct source term for generation of PA, which increases according to a Hill function of the active PKC density at the membrane (Fig 1A). To simplify and generalize the handling of receptor dynamics in this model, and considering that receptor activation is usually patterned by an Bepridil hydrochloride external ligand, we presume a steady gradient of occupied/active receptors, is the average receptor occupancy, expressed as a portion of a characteristic receptor density of 130 m-2, or 105/cell. The parameter is the relative steepness of the receptor occupancy gradient across the cell; for example, a value of = 0.1 corresponds to a 10% difference between the front and back of the cell. Stabilization of PLC recruitment by phosphatidic acid (PFL 1), combined with neutralization of MARCKS by PKC, promotes sensitive and strong gradient sensing Considering the network depicted in Fig 1A, with PFL 1 but not PFL 2, we evaluated the ability of receptor occupancy gradients (characterized by midpoint occupancy and % steepness) to polarize DAG and active PKC. For each of five gradient steepness values, ranging from 0% (uniform activation) up to 67% (2-fold) difference across the cell, simulations were run varying the value of the midpoint receptor occupancy, (Fig 2A). In some simulations, the spatial pattern oscillated, in which case the maximum and minimum values of the oscillation at each end of the cell are plotted. For examples of the simulated time courses, showing the transient behavior with sustained oscillations where relevant, observe S1 Fig and S2 Fig The PKC activity pattern was reversible for all but one of these simulated conditions. The exception is usually marked with an asterisk in Fig 2A, signifying lack of reversibility here and in subsequent figures of this paper. Open in a separate windows Fig 2 Gradient amplification by PFL 1 combined with regulation of MARCKS.(A) The concentration of active PKC molecules at the front (reddish circle) and back (blue circle) of the cell are plotted as a function of the mean fractional occupancy of receptors, where.