Investigating Differential Protein Expression in OLFR558 KO and WT Kidneys

Premenopausal women have blood pressure that is ~10mmHg lower than age-matched men. A study from our lab found that an olfactory receptor (OLFR558) is required for sex differences in blood pressure, as sex differences in blood pressure are entirely absent in Olfr558 knockout mice (Xu et al Science Advances 2024). However, there is a gap in our knowledge regarding how OLFR558 influences blood pressure, and, in the mechanism underlying the blood pressure differences between the sexes. We hypothesize that sex-specific differential protein expression between Olfr558 wild-type and knockout mice will yield novel insights into mechanisms driving sex differences in blood pressure. To pursue this, we collected kidneys from 8–9-week-old Olfr558 wild-type and knockout mice of both sexes for unbiased whole kidney proteomics (C57Bl6J; n=8 per genotype/sex). Whole kidney protein lysates were generated and sent to the Mass Spectrometry and Proteomics Core at JHU for TMTpro 16plex analysis (two plates; n=16 per plate). After filtering for proteins with an isolation interference of <30%, one protein group, and excluding spectra with at least one missing value and/or missing protein information, we found that the two plates shared 7,750 proteins. In addition, Plate 1 had 998 and Plate 2 had 972 unique proteins. To gain insight into why wild-type but not knockout mice display sex differences in blood pressure, we examined sex differences in protein expression. We first compared Olfr558 wild-type kidney samples (n=8 female vs n=8 males) and found 1,060 proteins which were differentially expressed by sex (p-value<0.05; log 2 fold change +/- 0.26). Of these 1,060 proteins which are differentially regulated by sex in wild-type mice, 865 were similarly differentially expressed by sex in knockout mice. However, there are 195 proteins that are differentially regulated by sex in wild-type but not knockout mice (female/male: 113 upregulated proteins, and 82 downregulated proteins). Preliminary pathway analysis indicates that a subset of these 195 proteins belong to endoplasmic reticulum proteins, some of which are associated with lipids. Conversely, we found that knockout mice have 776 proteins which are differentially expressed by sex in knockout but not wild-type kidneys (female/male: 501 upregulated proteins and 275 downregulated proteins). Based on pathway analysis, knockout mice have unique expression changes in proteins that correlate with cellular components including the ER membrane complex, cytoplasmic ribosomal proteins, mitochondrial respiratory chain complex III, and oligosaccharyltransferase complex, and, biological processes including protein insertion into ER membrane by stop-transfer membrane-anchor sequence. Better understanding of the relationship between sex hormones, blood pressure, and OLFR558 is pertinent to how physicians treat elevated blood pressure in men and women. JLP is supported by the American Heart Association Established Investigator Award, R21AG081683, R01DK139021, and R01DK137762. ADM is supported by NIH PREP grant R25GM109441 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.