Elevated level of HSPA1L mRNA correlates with graft-versus-host disease

Review of Genetic Variation as a Predictive Biomarker for Chronic Graft-Versus-Host-Disease After Allogeneic Stem Cell Transplantation

Chronic graft-versus-host disease (cGvHD) is one of the major complications of allogeneic stem cell transplantation (HSCT). cGvHD is an autoimmune-like disorder affecting multiple organs and involves a dermatological rash, tissue inflammation and fibrosis. The incidence of cGvHD has been reported to be as high as 30% to 60% and there are currently no reliable tools for predicting the occurrence of cGvHD. There is therefore an important unmet clinical need for predictive biomarkers. The present review summarizes the state of the art for genetic variation as a predictive biomarker for cGvHD. We discuss three different modes of action for genetic variation in transplantation: genetic associations, genetic matching, and pharmacogenetics. The results indicate that currently, there are no genetic polymorphisms or genetic tools that can be reliably used as validated biomarkers for predicting cGvHD. A number of recommendations for future studies can be drawn. The majority of studies to date have been under-powered and included too few patients and genetic markers. Like in all complex multifactorial diseases, large collaborative genome-level studies are now needed to achieve reliable and unbiased results. Some of the candidate genes, in particular, CTLA4, HSPE, IL1R1, CCR6, FGFR1OP, and IL10, and some non-HLA variants in the HLA gene region have been replicated to be associated with cGvHD risk in independent studies. These associations should now be confirmed in large well-characterized cohorts with fine mapping. Some patients develop cGvHD despite very extensive immunosuppression and other treatments, indicating that the current therapeutic regimens may not always be effective enough. Hence, more studies on pharmacogenetics are also required. Moreover, all of these studies should be adjusted for diagnostic and clinical features of cGvHD. We conclude that future studies should focus on modern genome-level tools, such as machine learning, polygenic risk scores and genome-wide association study-transcription meta-analyses, instead of focusing on just single variants. The risk of cGvHD may be related to the summary level of immunogenetic differences, or whole genome histocompatibility between each donor-recipient pair. As the number of genome-wide analyses in HSCT is increasing, we are approaching an era where there will be sufficient data to incorporate these approaches in the near future.

MAPKAP kinase 2-mediated phosphorylation of HspA1L protects male germ cells from heat stress-induced apoptosis

Developing male germ cells are extremely sensitive to heat stress; consequently, anatomic and physiologic adaptations have evolved to maintain proper thermoregulation during mammalian spermatogenesis. At the cellular level, increased expression and activity of HSP70 family members occur in response to heat stress in order to refold partially denatured proteins and restore function. In addition, several kinase-mediated signaling pathways are activated in the testis upon hyperthermia. The p38 MAP kinase (MAPK) pathway plays an important role in mitigating heat stress, and recent findings have implicated the downstream p38 substrate, MAPKAP kinase 2 (MK2), in this process. However, the precise function that this kinase plays in spermatogenesis is not completely understood. Using a proteomics-based screen, we identified and subsequently validated that the testis-enriched HSP70 family member, HspA1L, is a novel substrate of MK2. We demonstrate that MK2 phosphorylates HspA1L solely on Ser241, a residue within the N-terminal nucleotide-binding domain of the enzyme. This phosphorylation event enhances the chaperone activity of HspA1L in vitro and renders male germ cells more resistant to heat stress-induced apoptosis. Taken together, these findings illustrate a novel stress-induced signaling cascade that promotes the chaperone activity of HspA1L with implications for understanding male reproductive biology.

Role of HSPA1L as a cellular prion protein stabilizer in tumor progression via HIF-1α/GP78 axis

The cellular prion protein (PrP^C) is associated with metastasis, tumor progression and recurrence; however, the precise mechanisms underlying its action is not well understood. Our study found that PrP^C degradation decreased tumor progression in colorectal cancer (CRC). In a CRC cell line and human CRC tissue exposed to hypoxia, induced heat-shock 70-kDa protein-1-like (HSPA1L) expression stabilized hypoxia-inducible factor-1α (HIF-1α) protein and promoted PrP^C accumulation and tumorigenicity in vivo. PrP^C was degraded via the proteasome pathway mediated by the ubiquitin-protein E3 ligase glycoprotein 78 (GP78), which interacts directly with PrP^C. However, hypoxia-induced HSPA1L interacted with GP78 and inhibited its functions. HSPA1L knockdown facilitated the interaction of GP78 and PrP^C, thereby increasing PrP^C ubiquitination. Thus, GP78 was identified as the ubiquitinase for PrP^C, thereby revealing an essential mechanism that controls PrP^C levels in CRC. Our results suggest that the HSPA1L/HIF-1α/GP78 axis has a crucial role in PrP^C accumulation during tumor progression.

Heat Shock 70 Protein Genes and Genetic Susceptibility to Apical Periodontitis

INTRODUCTION

Heat shock proteins (HSPs) protect cells under adverse conditions such as infection, inflammation, and disease. The differential expression of HSPs in human periapical granulomas suggests a potential role for these proteins in periapical lesion development, which may contribute to different clinical outcomes. Therefore, we hypothesized that polymorphisms in HSP genes leading to perturbed gene expression and protein function may contribute to an individual's susceptibility to periapical lesion development.

METHODS

Subjects with deep carious lesions with or without periapical lesions (≥3 mm) were recruited at the University of Texas School of Dentistry at Houston and at the University of Pittsburgh. Genomic DNA samples of 400 patients were sorted into 2 groups: 183 cases with deep carious lesions and periapical lesions (cases) and 217 cases with deep carious lesions but without periapical lesions (controls). Eight single nucleotide polymorphisms (SNPs) in HSPA4, HSPA6, HSPA1L, HSPA4L, and HSPA9 genes were selected for genotyping. Genotypes were generated by end point analysis by using Taqman chemistry in a real-time polymerase chain reaction assay. Allele and genotype frequencies were compared among cases and controls by using χ(2) and Fisher exact tests as implemented in PLINK v.1.07. In silico analysis of SNP function was performed by using Polymorphism Phenotyping V2 and MirSNP software.

RESULTS

Overall, SNPs in HSPA1L and HSPA6 showed significant allelic association with cases of deep caries and periapical lesions (P < .05). We also observed altered transmission of HSPA1L SNP haplotypes (P = .03). In silico analysis of HSPA1L rs2075800 function showed that this SNP results in a glutamine-to-lysine substitution at position 602 of the protein and might affect the stability and function of the final protein.

CONCLUSIONS

Variations in HSPA1L and HSPA6 may be associated with periapical lesion formation in individuals with untreated deep carious lesions. Future studies could help predict host susceptibility to developing apical periodontitis.