Details for: CL4030011

Cell ID: CL4030011

Cell Name: epithelial cell of proximal tubule segment 3

Description: A brush border cell that is part of segment 3 (S3) of the proximal tubule epithelium, which extends from the medullary rays of the renal cortex into the outer medulla.

Synonyms: epithelial cell of segment 3 of proximal tubule

Selected Context(s): Overall

Gene Significance Landscape

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Cell Significance Index (CSI) is uniquely calculated to reveal cell-specific gene markers. More info here

Significant Genes List

Genes with the highest and lowest Percentile Rank Scores (PRS) for epithelial cell of proximal tubule segment 3 within the selected context(s).

Gene ID: A unique numerical identifier for this specific gene.
Symbol: Shortened abbreviation or name that represents this gene.
Ensembl Gene ID: A unique identifier assigned by Ensembl for genomic data mapping.
CSI Score: A combined effect size and statistical significance measure for epithelial cell of proximal tubule segment 3. Higher scores indicate a stronger, more significant difference in expression.
(Previously described as "Fold Change", but now represents Cliff's Delta × –log10(p).)

Gene ID: A unique numerical identifier for this specific gene.
Symbol: Shortened abbreviation or name that represents this gene.
Ensembl Gene ID: A unique identifier assigned by Ensembl for genomic data mapping.
CSI Score: A combined effect size and statistical significance measure for epithelial cell of proximal tubule segment 3. Higher scores indicate a stronger, more significant difference in expression.
Average CSI: csi sum / gene count
Cell network configuration

This network visualizes key genes for epithelial cell of proximal tubule segment 3. It primarily includes:
1. Top genes highly significant for this cell (Num. Top Cell Genes - based on the 'Min. CSI' setting).
2. Any additional specific 'Context Genes' you add below.
The final network is a combined view. Choose an Interaction Source (pathways or protein interactions) and optionally compare CSI scores with a Baseline Cell Type.

Maximum number of selected genes.
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Select a context for the target cell.
Target Cell for CSI:  epithelial cell of proximal tubule segment 3 (CL4030011)

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Nodes (Genes):
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Node size also reflects Target Cell CSI magnitude.
Node Color (Target Cell CSI in specific network):
 Very High
 High
 Medium
 Low
 Very Low
 N/A or Not Sig.
Edges (Interactions):
 STRING (Protein-Protein)
 ONTOLOGY (Shared Pathway)
 Colors vary by pathway category; default arrow applies.

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## Summary The [epithelial cell of proximal tubule segment 3](/details-cell/CL4030011) is a specialized brush border cell located in the S3 segment of the kidney's proximal tubule. Based on its gene significance profile, this cell type is overwhelmingly characterized by an exceptionally high and specific expression of genes involved in mitochondrial oxidative phosphorylation. This signature suggests that its primary role is centered around massive ATP production via aerobic respiration, likely to fuel the intensive active transport processes essential for renal reabsorption and secretion that occur in this nephron segment. ## Key Characteristics and Function The functional identity of the [epithelial cell of proximal tubule segment 3](/details-cell/CL4030011) is dominated by its metabolic machinery. An analysis of its top marker genes in the **Overall** context reveals distinct functional clusters. * **Mitochondrial Bioenergetics:** The most significant defining markers for this cell are core components of the mitochondrial electron transport chain. Genes encoding subunits of Complex IV ([COX2](/details-gene/4513) and [COX1](/details-gene/4512)), Complex III ([CYTB](/details-gene/4519)), Complex I ([ND5](/details-gene/4540), [ND4](/details-gene/4538), [ND3](/details-gene/4537), [ND1](/details-gene/4535), [ND4L](/details-gene/4539), and [ND2](/details-gene/4536)), and Complex V ([ATP6](/details-gene/4508) and [ATP8](/details-gene/4509)) all exhibit exceptionally high CSI (Z-SCORE) values. This collective signature underscores a profound specialization for aerobic respiration and ATP synthesis, positioning these cells as the primary energy powerhouses of the renal cortex and outer medulla. The high specificity of these markers suggests this metabolic capacity is a key feature distinguishing S3 segment cells from other renal cell types. * **Metabolic Processing and Detoxification:** Beyond energy production, this cell type expresses a suite of genes involved in specific metabolic pathways. Significant markers include [HIBCH](/details-gene/26275) and [ALDH6A1](/details-gene/4329), which participate in branched-chain amino acid catabolism. The expression of [FBP1](/details-gene/2203) points to a role in gluconeogenesis, a critical renal function. Furthermore, genes like [GPX3](/details-gene/2878) (glutathione peroxidase) and [MSRA](/details-gene/4482) (methionine sulfoxide reductase) indicate a robust system for managing oxidative stress, which is likely a necessary adaptation to the high rate of mitochondrial respiration and the potential for reactive oxygen species (ROS) generation. * **Lack of Immune Presentation:** The anti-marker profile provides critical insight into the functions this cell lacks. The negative CSI values for [B2M](/details-gene/567) (Beta-2-microglobulin) and [HLA C](/details-gene/3107), both essential components of the MHC class I antigen presentation pathway, are highly significant. This suggests that [epithelial cells of proximal tubule segment 3](/details-cell/CL4030011) have a constitutively low level of immune surveillance activity, potentially to prevent autoimmune responses against renal tissues under normal physiological conditions. ## Clinical Significance and Contextual Roles The profound reliance of the [epithelial cell of proximal tubule segment 3](/details-cell/CL4030011) on oxidative phosphorylation makes it a key player in both renal health and disease. **Overall**, the cell's gene expression profile highlights its vulnerability to conditions that disrupt mitochondrial function or oxygen supply. Ischemic events, such as those occurring during acute kidney injury (AKI), would likely compromise these cells first due to their high oxygen demand. Similarly, genetic mitochondrial diseases resulting from mutations in any of its top marker genes (e.g., [COX1](/details-gene/4512), [ND5](/details-gene/4540)) would be expected to manifest with severe renal dysfunction, given this cell's critical role in tubular transport. The high expression of antioxidant enzymes like [GPX3](/details-gene/2878), which has been linked to kidney function and blood pressure regulation ([Link](https://pubmed.ncbi.nlm.nih.gov/1339300/)), suggests this cell is a primary site for defense against oxidative damage in the kidney, a central mechanism in diabetic nephropathy and chronic kidney disease. ## Potential Mechanisms and Research Directions 1. **Hypothesis:** The extreme metabolic specialization of the [epithelial cell of proximal tubule segment 3](/details-cell/CL4030011) on aerobic respiration renders it highly susceptible to hypoxic/ischemic injury and makes it a critical determinant of the severity of acute kidney injury (AKI). * **Surprising Findings:** The extremely low significance of [LDHA](/details-gene/3939), a key enzyme in anaerobic glycolysis, is notable. This suggests that these cells may have a very limited capacity to generate ATP under anaerobic conditions, making them exceptionally vulnerable when oxygen supply is compromised. * **Testable Questions:** How does the metabolic profile (e.g., oxygen consumption rate, lactate production) of isolated [epithelial cells of proximal tubule segment 3](/details-cell/CL4030011) change in response to graded hypoxia compared to epithelial cells from other nephron segments? 2. **Hypothesis:** The constitutively low expression of MHC class I machinery ([B2M](/details-gene/567), [HLA C](/details-gene/3107)) in [epithelial cells of proximal tubule segment 3](/details-cell/CL4030011) creates a state of relative immune privilege, which may be a protective mechanism to limit inflammation but could also make this segment a potential reservoir for persistent viral infections of the kidney. * **Surprising Findings:** It is counterintuitive for a barrier epithelial cell to have such a diminished antigen presentation signature. This suggests that immune monitoring in this specific renal microenvironment may be delegated to resident immune cells or is actively suppressed to maintain organ function. * **Testable Questions:** Can stimulation with pro-inflammatory cytokines, such as IFN-gamma, induce a significant upregulation of [B2M](/details-gene/567) and MHC class I surface expression on these cells, or is the pathway genetically or epigenetically repressed?