The Role of Sfp1 in Candida albicans Cell Wall Maintenance.

The cell wall is the first interface for Candida albicans interaction with the surrounding environment and the host cells. Therefore, maintenance of cell wall integrity (CWI) is crucial for C. albicans survival and host-pathogen interaction. In response to environmental stresses, C. albicans undergoes cell wall remodeling controlled by multiple signaling pathways and transcription regulators. Here, we explored the role of the transcription factor Sfp1 in CWI. A deletion of the SFP1 gene not only caused changes in cell wall properties, cell wall composition and structure but also modulated expression of cell wall biosynthesis and remodeling genes. In addition, Cas5 is a known transcription regulator for C. albicans CWI and cell wall stress response. Interestingly, our results indicated that Sfp1 negatively controls the CAS5 gene expression by binding to its promoter element. Together, this study provides new insights into the regulation of C. albicans CWI and stress response.

A Comparison of Numerical and Actual Measurements of Large-Scale Rib-Structured Pallet Flatness Using Recycled Polypropylene in Injection Molding.

Many challenges are associated with the injection molding process for forming a rib-structured pallet (1100 mm × 1100 mm × 140 mm, length × width × height) because greater flowing resistance through the rib channels within the pallet can induce insufficient filling. Essentially, multi-gate filling involves a sequential valve gate system, which helps to spread the filling front with fewer weld lines. Based on the presetting of the sequential scheme of the valve gates, actual measurements of pallet flatness using the ATOS scan system were compared to numerical warpage measurements of a pallet derived by Moldex3D 2020. In this study, we propose a sequential scheme by actuating the valve gates to open once the flow front spreads towards them; then, actual warpage measurements of a pallet are compared with numerical measurements. The results show that the warpage of the top surface of the pallet is 5.144 mm in actual measurements and 5.729 mm in simulation. The results all indicated small warpage with respect to the pallet size. The simulation and actual measurements of flatness are in excellent agreement; the difference in top flatness between the simulated and actual pallet is 0.59 mm, while the bottom flatness difference is 0.035 mm. By adjusting the cooling water temperature, increasing the mold temperature, and decreasing the material temperature, overall flatness and warpage displacement can be reduced.

Investigation of the Warpage of a High-Density Polyethylene Pallet by Plastic Injection Compression Molding: Part I-Numerical Approach.

Many challenges are associated with the injection compression molding process for producing a half-pallet (1320 mm × 1110 mm × 75 mm, length × width × height), which is butt-welded to another one for enhancing its strength. This pooled high-density polyethylene (HDPE) pallet is able to endure the impacts of a heavy load and a low ambient temperature. Reducing the warpage of a half-pallet is, therefore, essential for reducing the residual internal stress within the welded portions. An advanced Moldex3D package helps to detail the temperature distribution and warpage of a half-pallet. The pre-setting molding parameters from a mass-production factory produce half-pallets with worse flatness. In this investigation on using appropriate cooling water temperatures within the core and cavity plates of the mold, the numerical results show that the warpage of the top surface of the half-pallet was 11.549 mm, low warpage with respect to this large-scale pallet. Furthermore, the compression speed of 50-60 mm/s may have produced a low flatness of the half-pallet in this study.

Candida albicans Sfp1 Is Involved in the Cell Wall and Endoplasmic Reticulum Stress Responses Induced by Human Antimicrobial Peptide LL-37.

Candida albicans is a commensal fungus of humans but can cause infections, particularly in immunocompromised individuals, ranging from superficial to life-threatening systemic infections. The cell wall is the outermost layer of C. albicans that interacts with the host environment. Moreover, antimicrobial peptides (AMPs) are important components in innate immunity and play crucial roles in host defense. Our previous studies showed that the human AMP LL-37 binds to the cell wall of C. albicans, alters the cell wall integrity (CWI) and affects cell adhesion of this pathogen. In this study, we aimed to further investigate the molecular mechanisms underlying the C. albicans response to LL-37. We found that LL-37 causes cell wall stress, activates unfolded protein response (UPR) signaling related to the endoplasmic reticulum (ER), induces ER-derived reactive oxygen species and affects protein secretion. Interestingly, the deletion of the SFP1 gene encoding a transcription factor reduced C. albicans susceptibility to LL-37, which is cell wall-associated. Moreover, in the presence of LL-37, deletion of SFP1 attenuated the UPR pathway, upregulated oxidative stress responsive (OSR) genes and affected bovine serum albumin (BSA) degradation by secreted proteases. Therefore, these findings suggested that Sfp1 positively regulates cell wall integrity and ER homeostasis upon treatment with LL-37 and shed light on pathogen-host interactions.