Controller adherence following hospital discharge in high risk children: A pilot randomized trial of text message reminders.

OBJECTIVE: To assess the feasibility of a mobile health, inhaled corticosteroid (ICS) adherence reminder intervention and to characterize adherence trajectories immediately following severe asthma exacerbation in high-risk urban children with persistent asthma. METHODS: Children aged 2-13 with persistent asthma were enrolled in this pilot randomized controlled trial during an asthma emergency department (ED) visit or hospitalization. Intervention arm participants received daily text message reminders for 30 days, and both arms received electronic sensors to measure ICS use. Primary outcomes were feasibility of sensor use and text message acceptability. Secondary outcomes included adherence to prescribed ICS regimen and 30-day adherence trajectories. Group-based trajectory modeling was used to examine adherence trajectories. RESULTS: Forty-one participants (mean age 5.9) were randomized to intervention (n = 21) or control (n = 20). Overall, 85% were Black, 88% had public insurance, and 51% of the caregivers had a high school education or less. Thirty-two participant families (78%) transmitted medication adherence data; of caregivers who completed the acceptability survey, 25 (96%) chose to receive daily reminders beyond that study interval. Secondary outcome analyses demonstrated similar average daily adherence between groups (intervention = 36%; control = 32%, P = 0.73). Three adherence trajectories were identified with none ever exceeding 80% adherence. CONCLUSIONS: Within a high-risk pediatric cohort, electronic monitoring of ICS use and adherence reminders delivered via text message were feasible for most participants, but there was no signal of effect. Adherence trajectories following severe exacerbation were suboptimal, demonstrating an important opportunity for asthma care improvement.

Signaling through Lrg1, Rho1 and Pkc1 Governs Candida albicans Morphogenesis in Response to Diverse Cues.

The capacity to transition between distinct morphological forms is a key virulence trait for diverse fungal pathogens. A poignant example of a leading opportunistic fungal pathogen of humans for which an environmentally responsive developmental program underpins virulence is Candida albicans. C. albicans mutants that are defective in the transition between yeast and filamentous forms typically have reduced virulence. Although many positive regulators of C. albicans filamentation have been defined, there are fewer negative regulators that have been implicated in repression of filamentation in the absence of inducing cues. To discover novel negative regulators of filamentation, we screened a collection of 1,248 C. albicans homozygous transposon insertion mutants to identify those that were filamentous in the absence of inducing cues. We identified the Rho1 GAP Lrg1, which represses filamentous growth by stimulating Rho1 GTPase activity and converting Rho1 to its inactive, GDP-bound form. Deletion of LRG1 or introduction of a RHO1 mutation that locks Rho1 in constitutively active, GTP-bound state, leads to filamentation in the absence of inducing cues. Deletion of the Rho1 downstream effector PKC1 results in defective filamentation in response to diverse host-relevant inducing cues, including serum. We further established that Pkc1 is not required to sense filament-inducing cues, but its kinase activity is critical for the initiation of filamentous growth. Our genetic analyses revealed that Pkc1 regulates filamentation independent of the canonical MAP kinase cascade. Further, although Ras1 activation is not impaired in a pkc1Δ/pkc1Δ mutant, adenylyl cyclase activity is reduced, consistent with a model in which Pkc1 functions in parallel with Ras1 in regulating Cyr1 activation. Thus, our findings delineate a signaling pathway comprised of Lrg1, Rho1 and Pkc1 with a core role in C. albicans morphogenesis, and illuminate functional relationships that govern activation of a central transducer of signals that control environmental response and virulence programs.

Opportunistic yeast pathogens: reservoirs, virulence mechanisms, and therapeutic strategies.

Life-threatening invasive fungal infections are becoming increasingly common, at least in part due to the prevalence of medical interventions resulting in immunosuppression. Opportunistic fungal pathogens of humans exploit hosts that are immunocompromised, whether by immunosuppression or genetic predisposition, with infections originating from either commensal or environmental sources. Fungal pathogens are armed with an arsenal of traits that promote pathogenesis, including the ability to survive host physiological conditions and to switch between different morphological states. Despite the profound impact of fungal pathogens on human health worldwide, diagnostic strategies remain crude and treatment options are limited, with resistance to antifungal drugs on the rise. This review will focus on the global burden of fungal infections, the reservoirs of these pathogens, the traits of opportunistic yeast that lead to pathogenesis, host genetic susceptibilities, and the challenges that must be overcome to combat antifungal drug resistance and improve clinical outcome.

Regenerative Peripheral Nerve Interface for Prostheses Control: Electrode Comparison.

BACKGROUND: This study compared epimysial patch electrodes with intramuscular hook electrodes using monopolar and bipolar recording configurations. The purpose was to determine which strategy transduced muscle signals with better fidelity for control of myoelectric prostheses. METHODS: One of the two electrode styles, patch (n = 4) or hook (n = 6) was applied to the left extensor digitorum longus muscle in rats. Electrodes were evaluated at the time of placement and at monthly intervals for 4 months. Evaluations consisted of evoked electromyography signals from stimulation pulses applied to the peroneal and tibial nerves in both monopolar and bipolar recording configurations. RESULTS: Compared with hook electrodes, patch electrodes recorded larger signals of interest and minimized muscle tissue injury. A bipolar electrode configuration significantly reduced signal noise when compared with a monopolar configuration. CONCLUSION: Epimysial patch electrodes outperform intramuscular hook electrodes during chronic skeletal muscle implantation.

A culture system to study oligodendrocyte myelination processes using engineered nanofibers.

Current methods for studying central nervous system myelination necessitate permissive axonal substrates conducive to myelin wrapping by oligodendrocytes. We have developed a neuron-free culture system in which electron-spun nanofibers of varying sizes substitute for axons as a substrate for oligodendrocyte myelination, thereby allowing manipulation of the biophysical elements of axonal-oligodendroglial interactions. To investigate axonal regulation of myelination, this system effectively uncouples the role of molecular (inductive) cues from that of biophysical properties of the axon. We use this method to uncover the causation and sufficiency of fiber diameter in the initiation of concentric wrapping by rat oligodendrocytes. We also show that oligodendrocyte precursor cells display sensitivity to the biophysical properties of fiber diameter and initiate membrane ensheathment before differentiation. The use of nanofiber scaffolds will enable screening for potential therapeutic agents that promote oligodendrocyte differentiation and myelination and will also provide valuable insight into the processes involved in remyelination.

Membrane fluidity and temperature sensing are coupled via circuitry comprised of Ole1, Rsp5, and Hsf1 in Candida albicans.

Temperature is a ubiquitous environmental variable which can profoundly influence the physiology of living cells as it changes over time and space. When yeast cells are exposed to a sublethal heat shock, normal metabolic functions become repressed and the heat shock transcription factor Hsf1 is activated, inducing heat shock proteins (HSPs). Candida albicans, the most prevalent human fungal pathogen, is an opportunistic pathogen that has evolved as a relatively harmless commensal of healthy individuals. Even though C. albicans occupies thermally buffered niches, it has retained the classic heat shock response, activating Hsf1 during slow thermal transitions such as the increases in temperature suffered by febrile patients. However, the mechanism of temperature sensing in fungal pathogens remains enigmatic. A few studies with Saccharomyces cerevisiae suggest that thermal stress is transduced into a cellular signal at the level of the membrane. In this study, we manipulated the fluidity of C. albicans membrane to dissect mechanisms of temperature sensing. We determined that in response to elevated temperature, levels of OLE1, encoding a fatty acid desaturase, decrease. Subsequently, loss of OLE1 triggers expression of FAS2, encoding a fatty acid synthase. Furthermore, depletion of OLE1 prevents full activation of Hsf1, thereby reducing HSP expression in response to heat shock. This reduction in Hsf1 activation is attributable to the E3 ubiquitin ligase Rsp5, which regulates OLE1 expression. To our knowledge, this is the first study to define a molecular link between fatty acid synthesis and the heat shock response in the fungal kingdom.

Synthesis, copolymerization and peptide-modification of carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) for neural electrode interfaces.

BACKGROUND: Conjugated polymers have been developed as effective materials for interfacing prosthetic device electrodes with neural tissue. Recent focus has been on the development of conjugated polymers that contain biological components in order to improve the tissue response upon implantation of these electrodes. METHODS: Carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) monomer was synthesized in order to covalently bind peptides to the surface of conjugated polymer films. EDOTacid was copolymerized with EDOT monomer to form stable, electrically conductive copolymer films referred to as PEDOT-PEDOTacid. The peptide GGGGRGDS was bound to PEDOT-PEDOTacid to create peptide functionalized PEDOT films. RESULTS: The PEDOT-PEDOTacid-peptide films increased the adhesion of primary rat motor neurons between 3 and 9 times higher than controls, thus demonstrating that the peptide maintained its biological activity. CONCLUSIONS: The EDOT-acid monomer can be used to create functionalized PEDOT-PEDOTacid copolymer films that can have controlled bioactivity. GENERAL SIGNIFICANCE: PEDOT-PEDOTacid-peptide films have the potential to control the behavior of neurons and vastly improve the performance of implanted electrodes. This article is part of a Special Issue entitled Organic Bioelectronics-Novel Applications in Biomedicine.

Hsp90 orchestrates transcriptional regulation by Hsf1 and cell wall remodelling by MAPK signalling during thermal adaptation in a pathogenic yeast.

Thermal adaptation is essential in all organisms. In yeasts, the heat shock response is commanded by the heat shock transcription factor Hsf1. Here we have integrated unbiased genetic screens with directed molecular dissection to demonstrate that multiple signalling cascades contribute to thermal adaptation in the pathogenic yeast Candida albicans. We show that the molecular chaperone heat shock protein 90 (Hsp90) interacts with and down-regulates Hsf1 thereby modulating short term thermal adaptation. In the longer term, thermal adaptation depends on key MAP kinase signalling pathways that are associated with cell wall remodelling: the Hog1, Mkc1 and Cek1 pathways. We demonstrate that these pathways are differentially activated and display cross talk during heat shock. As a result ambient temperature significantly affects the resistance of C. albicans cells to cell wall stresses (Calcofluor White and Congo Red), but not osmotic stress (NaCl). We also show that the inactivation of MAP kinase signalling disrupts this cross talk between thermal and cell wall adaptation. Critically, Hsp90 coordinates this cross talk. Genetic and pharmacological inhibition of Hsp90 disrupts the Hsf1-Hsp90 regulatory circuit thereby disturbing HSP gene regulation and reducing the resistance of C. albicans to proteotoxic stresses. Hsp90 depletion also affects cell wall biogenesis by impairing the activation of its client proteins Mkc1 and Hog1, as well as Cek1, which we implicate as a new Hsp90 client in this study. Therefore Hsp90 modulates the short term Hsf1-mediated activation of the classic heat shock response, coordinating this response with long term thermal adaptation via Mkc1- Hog1- and Cek1-mediated cell wall remodelling.

Stress adaptation in a pathogenic fungus.

Candida albicans is a major fungal pathogen of humans. This yeast is carried by many individuals as a harmless commensal, but when immune defences are perturbed it causes mucosal infections (thrush). Additionally, when the immune system becomes severely compromised, C. albicans often causes life-threatening systemic infections. A battery of virulence factors and fitness attributes promote the pathogenicity of C. albicans. Fitness attributes include robust responses to local environmental stresses, the inactivation of which attenuates virulence. Stress signalling pathways in C. albicans include evolutionarily conserved modules. However, there has been rewiring of some stress regulatory circuitry such that the roles of a number of regulators in C. albicans have diverged relative to the benign model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. This reflects the specific evolution of C. albicans as an opportunistic pathogen obligately associated with warm-blooded animals, compared with other yeasts that are found across diverse environmental niches. Our understanding of C. albicans stress signalling is based primarily on the in vitro responses of glucose-grown cells to individual stresses. However, in vivo this pathogen occupies complex and dynamic host niches characterised by alternative carbon sources and simultaneous exposure to combinations of stresses (rather than individual stresses). It has become apparent that changes in carbon source strongly influence stress resistance, and that some combinatorial stresses exert non-additive effects upon C. albicans. These effects, which are relevant to fungus-host interactions during disease progression, are mediated by multiple mechanisms that include signalling and chemical crosstalk, stress pathway interference and a biological transistor.

Comparison of Childless and Partnerless Vasectomy Rates Before and After Dobbs v. Jackson Women's Health Organization.

The Supreme Court ruling Dobbs v. Jackson Women's Health Organization (June 2022) overturned federal protection of abortion rights, resulting in significant impact on both male and female reproductive rights and health care delivery. We conducted a retrospective review of all patients who underwent vasectomy at a single academic institution between June 2021 and June 2023. Our objective was to compare the rates of childless and partnerless vasectomies 1 year before and after this ruling, as these men may be more susceptible to postprocedural regret. Of total, 631 men (median age = 39 years, range = 20-70) underwent vasectomy consultation. Total vasectomies pre- and post-Dobbs were 304 (48%) versus 327 (52%). Total childless and partnerless vasectomies pre- and post-Dobbs were 44 (42%) versus 61 (58%) and 43 (46%) versus 50 (54%). Vasectomy completion rate was slightly increased post-Dobbs (90% vs. 88%; p = .240). The post-Dobbs cohort had significantly less children (1.8 vs. 2.0; p = .031). Men in the post-Dobbs era were significantly more likely to be commercially insured (72% vs. 64%) and less likely to be uninsured (1% vs. 6%; p = .002). Men who underwent childless vasectomy were significantly more likely to be younger (36.4 vs. 39.8 years; p < .001). There was a significantly greater proportion of Hispanic and Black men in the partnerless cohort compared to the cohort with partners (24% vs. 19% and 9% vs. 2%; p = .002). In conclusion, patients should be counseled on the permanent nature of this procedure, underscoring need for effective and reversible male contraception.

Retreatment for Lower Urinary Tract Symptoms After Water Vapor Thermal Therapy.

OBJECTIVE: To identify predictors of retreatment for symptomatic recurrence among men who undergo water vapor thermal therapy (WVTT; Rezum, Boston Scientific, Marlborough, MA), a minimally invasive surgical treatment for lower urinary tract symptoms secondary to benign prostatic hyperplasia. METHODS: We retrospectively reviewed patients treated with WVTT at a single institution from August 2017 to February 2022. Patients who underwent a second benign prostatic hyperplasia procedure for persistent or recurrent lower urinary tract symptoms within 2years of original treatment were compared to the remaining cohort who did not undergo retreatment. Multivariate analysis was used to assess for predictors of retreatment. RESULTS: Data were obtained from 192 patients. 10 (5%) patients were retreated. The retreatment cohort had smaller prostate volumes (50.4±18.2 cc vs 48.5±35.7 cc; P = .003) and received a greater number of water vapor injections (4.4±1.8 vs 5.2±3.9; P < .001). At 6month follow-up, total International Prostate Symptom Score (IPSS; 10.13 ± 7.40 vs 18.5 ± 11.55, P = .044) and voiding subscores (4.59 ± 4.39 vs 9.5 ± 7.84, P = .006) were significantly worse in the retreatment group. On multivariate analysis, >1 treatment per lobe was independently associated with increased risk of retreatment (hazard ratio 8.509, 95% CI [1.109-65.293]; P = .039). CONCLUSION: WVTT has a low retreatment rate. Men who required retreatment received more injections and showed worsened voiding symptom scores 6months postoperatively. Decreasing the number of injections may help reduce treatment failure rates.

Posttranslational modifications of proteins in the pathobiology of medically relevant fungi.

Posttranslational modifications of proteins drive a wide variety of cellular processes in eukaryotes, regulating cell growth and division as well as adaptive and developmental processes. With regard to the fungal kingdom, most information about posttranslational modifications has been generated through studies of the model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, where, for example, the roles of protein phosphorylation, glycosylation, acetylation, ubiquitination, sumoylation, and neddylation have been dissected. More recently, information has begun to emerge for the medically important fungal pathogens Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans, highlighting the relevance of posttranslational modifications for virulence. We review the available literature on protein modifications in fungal pathogens, focusing in particular upon the reversible peptide modifications sumoylation, ubiquitination, and neddylation.

Highly Aligned Poly(3,4-ethylene dioxythiophene) (PEDOT) Nano- and Microscale Fibers and Tubes.

This study reports a facile method for the fabrication of aligned Poly(3,4-ethylene dioxythiophene) (PEDOT) fibers and tubes based on electrospinning and oxidative chemical polymerization. Discrete PEDOT nano- and microfibers and nano- and microtubes are difficult to fabricate quickly and reproducibly. We employed poly(lactide-co-glycolide) (PLGA) polymers that were loaded with polymerizable 3,4-ethylene dioxythiophene (EDOT) monomer to create aligned nanofiber assemblies using a rotating glass mandrel during electrospinning. The EDOT monomer/PLGA polymer blends were then polymerized by exposure to an oxidative catalyst (FeCl3). PEDOT was polymerized by continuously dripping a FeCl3 solution onto the glass rod during electrospinning. The resulting PEDOT fibers were conductive, aligned and discrete. Fiber bundles could be easily produced in lengths of several centimeters. The PEDOT sheath/PLGA core fibers were immersed in chloroform to remove the PLGA and any residual EDOT resulting in hollow PEDOT tubes. This approach made it possible to easily generate large areas of aligned PEDOT fibers/tubes. The structure and properties of the aligned assemblies were measured using optical microscopy, electron microscopy, Raman spectroscopy, thermal gravimetric analysis, and DC conductivity measurements. We also demonstrated that the aligned PEDOT sheath/PLGA core fiber assemblies could be used in supporting and directing the extension of dorsal root ganglia (DRG) neurons in vitro.

Erector spinae plane blocks for analgesia after percutaneous nephrolithotomy A pathway to reduce opioids.

INTRODUCTION: Despite its minimally invasive nature, percutaneous nephrolithotomy (PCNL ) may be associated with significant pain. Challenges in pain control may prevent timely discharge (and expose patients to adverse effects of opioid use). We sought to evaluate whether our patients who underwent erector spinae plane (ESP) regional blocks experienced improved postoperative pain control and decreased opioid use after PCNL (compared with those who did not receive blocks). METHODS: We retrospectively reviewed consecutive PCNL cases on patients admitted for greater than 24 hours without pre-existing opioid regimens for chronic pain. Cases were completed by a single high-volume surgeon. Patients who accepted an ESP block were compared to those who did not receive a block. Patients received either a single injection or a disposable pump delivering intermittent boluses of ropivacaine 0.2%. Demographic and perioperative data were analyzed. The primary outcomes were opioid use measured in morphine milligram equivalent (MME ) and patient-reported pain scores during the first 24 hours of hospitalization. RESULTS: From March 2019 to August 2021, 44 patients were identified who met criteria - 28 of whom received an ESP block (including 14 continuous blocks). The patients who received blocks had significantly decreased opioid use (18.3 vs. 81.3 MME, p=0.004) and a longer mean time to first non-zero pain score (p=0.004). Continuous blocks had similar opioid use to single shot blocks (21.0 vs. 15.6 MME, p=0.952). CONCLUSIONS: ESP regional blocks appear to offer an effective adjunct method for pain control after PCNL and may reduce post-PCNL opioid use while maintaining adequate patient analgesia.

Molecular and proteomic analyses highlight the importance of ubiquitination for the stress resistance, metabolic adaptation, morphogenetic regulation and virulence of Candida albicans.

Post-translational modifications of proteins play key roles in eukaryotic growth, differentiation and environmental adaptation. In model systems the ubiquitination of specific proteins contributes to the control of cell cycle progression, stress adaptation and metabolic reprogramming. We have combined molecular, cellular and proteomic approaches to examine the roles of ubiquitination in Candida albicans, because little is known about ubiquitination in this major fungal pathogen of humans. Independent null (ubi4/ubi4) and conditional (MET3p-UBI4/ubi4) mutations were constructed at the C. albicans polyubiquitin-encoding locus. These mutants displayed morphological and cell cycle defects, as well as sensitivity to thermal, oxidative and cell wall stresses. Furthermore, ubi4/ubi4 cells rapidly lost viability under starvation conditions. Consistent with these phenotypes, proteins with roles in stress responses (Gnd1, Pst2, Ssb1), metabolism (Acs2, Eno1, Fba1, Gpd2, Pdx3, Pgk1, Tkl1) and ubiquitination (Ubi4, Ubi3, Pre1, Pre3, Rpt5) were among the ubiquitination targets we identified, further indicating that ubiquitination plays key roles in growth, stress responses and metabolic adaptation in C. albicans. Clearly ubiquitination plays key roles in the regulation of fundamental cellular processes that underpin the pathogenicity of this medically important fungus. This was confirmed by the observation that the virulence of C. albicans ubi4/ubi4 cells is significantly attenuated.

Combining topographical and genetic cues to promote neuronal fate specification in stem cells.

There is little remedy for the devastating effects resulting from neuronal loss caused by neural injury or neurodegenerative disease. Reconstruction of damaged neural circuitry with stem cell-derived neurons is a promising approach to repair these defects, but controlling differentiation and guiding synaptic integration with existing neurons remain significant unmet challenges. Biomaterial surfaces can present nanoscale topographical cues that influence neuronal differentiation and process outgrowth. By combining these scaffolds with additional molecular biology strategies, synergistic control over cell fate can be achieved. Here, we review recent progress in promoting neuronal fate using techniques at the interface of biomaterial science and genetic engineering. New data demonstrates that combining nanofiber topography with an induced genetic program enhances neuritogenesis in a synergistic fashion. We propose combining patterned biomaterial surface cues with prescribed genetic programs to achieve neuronal cell fates with the desired sublineage specification, neurochemical profile, targeted integration, and electrophysiological properties.

Early results of surgical intervention for elbow deformity in cerebral palsy based on degree of contracture.

PURPOSE: Elbow flexion posture, caused by spasticity of the muscles on the anterior surface of the elbow, is the most common elbow deformity seen in patients with cerebral palsy. This study retrospectively evaluated early results of 2 surgical interventions for elbow flexion deformities based on degree of contracture. We hypothesized that by guiding surgical treatment to degree of preoperative contracture, elbow extension and flexion posture angle at ambulation could be improved while preserving maximum flexion. METHODS: Eighty-six patients (90 elbows) were treated for elbow spasticity due to cerebral palsy. Seventy-one patients (74 elbows) were available for follow-up. Fifty-seven patients with fixed elbow contractures less than 45° were surgically treated with a partial elbow muscle lengthening, which included partial lengthening of the biceps and brachialis and proximal release of the brachioradialis. Fourteen patients (17 elbows) with fixed elbow contractures ≥ 45° had a more extensive full elbow release, with biceps z-lengthening, partial brachialis myotomy, and brachioradialis proximal release. RESULTS: Age at surgery averaged 10 years (range, 3-20 y) for partial lengthening and 14 years (range, 5-20 y) for full elbow release. Follow-up averaged 22 months (range, 7-144 mo) for partial lengthening and 18 months (range, 6-51 mo) for full elbow release. Both groups achieved meaningful improvement in flexion posture angle at ambulation, active and passive extension, and total range of motion. Elbow flexion posture angle at ambulation improved by 57° and active extension increased 17° in the partial lengthening group, with a 4° loss of active flexion. In the full elbow release group, elbow flexion posture angle at ambulation improved 51° and active extension improved 38°, with a loss of 19° of active flexion. CONCLUSIONS: Surgical treatment of spastic elbow flexion in cerebral palsy can improve deformity. We obtained excellent results by guiding the surgical intervention by the amount of preoperative elbow contracture. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Evaluation of Risk Factors for Hepatitis C Virus Infection Among Philadelphia's Shelter-Bound, Homeless Population: Data from a Student-Run Hepatitis C Virus Screening Initiative.

The objective was to assess risk factors for HCV specific to the shelter-bound homeless population of Philadelphia, Pennsylvania. This is a retrospective analysis of data obtained from 306 patients who received HCV antibody testing at 4 homeless shelters in Philadelphia between March 2017 and June 2019. Risk factors for HCV infection specific to this population were analyzed using Fischer exact tests. Fourteen (4.6%) of 306 patients screened positive for HCV infection. Risk factors for HCV infection among this shelter-bound homeless population included injection drug use, inhalation drug use, and tattoos obtained while incarcerated. Although an estimated 2.8% of the population of Philadelphia is infected with HCV, 4.6% of those screened in this program tested positive, highlighting the increased prevalence of HCV among the shelter-bound homeless population and the importance of assessing risks for HCV infection inherent to this specific population.

Role of the heat shock transcription factor, Hsf1, in a major fungal pathogen that is obligately associated with warm-blooded animals.

All organisms have evolved mechanisms that protect them against environmental stress. The major fungal pathogen of humans, Candida albicans, has evolved robust stress responses that protect it against human immune defences and promote its pathogenicity. However, C. albicans is unlikely to be exposed to heat shock as it is obligatorily associated with warm-blooded animals. Therefore, we examined the role of the heat shock transcription factor (Hsf1) in this pathogen. We show that C. albicans expresses an evolutionarily conserved Hsf1 (orf19.4775) that is phosphorylated in response to heat shock, induces transcription via the heat shock element (HSE), contributes to the global transcriptional response to heat shock, and is essential for viability. Why has Hsf1 been conserved in this obligate animal saprophyte? We reasoned that Hsf1 might contribute to medically relevant stress responses. However, this is not the case, as an Hsf1-specific HSE-lacZ reporter is not activated by oxidative, osmotic, weak acid or pH stress. Rather, Hsf1 is required for the expression of essential chaperones in the absence of heat shock (e.g. Hsp104, Hsp90, Hsp70). Furthermore, Hsf1 regulates the expression of HSE-containing genes in response to growth temperature in C. albicans. Therefore, the main role of Hsf1 in this pathogen might be the homeostatic modulation of chaperone levels in response to growth temperature, rather than the activation of acute responses to sudden thermal transitions.