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STIM1 / Stromal interaction molecule 1 · IHC design guide
Design Immunohistochemistry for STIM1
Plan chromogenic STIM1 IHC in paraffin sections with cell-specific tissue controls and an IHC-validated antibody (HPA tissue IHC; datasheet A00312-1). Interpret variable cytoplasmic staining in light of STIM1’s ER and cell membrane localization (HPA tissue IHC; UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
STIM1 Immunohistochemistry Experimental Design Guide
Expected localisation, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before staining
| Expected localisation | Variable cytoplasmic staining (HPA tissue IHC); ER and cell membrane localization (UniProt) | |
| Staining pattern | Variable cytoplasmic staining in most tissues (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A00312-1) | |
| Positive control | Cerebellum+4 more · see all | |
| Negative control | Adipose tissue+3 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Calcium-store depletion can shift STIM1 to ER–membrane junctions (UniProt) | |
| Regulation | Intensity varies by cell type (HPA tissue IHC) | |
| Isoform / epitope | 2 isoforms; map the epitope to the extracellular or cytoplasmic region (UniProt) |
Section 1
Recommended STIM1 IHC & IF Protocols
The catalog antibody protocol uses heat-mediated EDTA pH 8.0 retrieval (datasheet A00312-1). The published options below report STIM1 staining in human oral tissue (PMC8739746) and tumor tissue sections (PMC10964627).
| Sample | Paraffin-embedded human breast cancer tissue; fixative not specified (datasheet A00312-1) |
| Fixation | Image fixative and duration unreported (datasheet A00312-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: EDTA pH 8.0 (datasheet A00312-1); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A00312-1) |
| Primary antibody | Rabbit anti-STIM1, 2-5 μg/ml (datasheet A00312-1) |
| Primary incubation | Overnight at 4 °C (datasheet A00312-1) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A00312-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | STIM1-positive staining in purkinje cells - cytoplasm/membrane of cerebellum (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression at variable levels in most tissues. No signal in the no-primary control. |
💡Decision noteStart with EDTA pH 8.0 for the catalog antibody (datasheet A00312-1). Low-pH citrate is a published alternative with a different STIM1 antibody (PMC10964627).
Section 2
What Is the Expected STIM1 Staining Pattern?
STIM1 is an endoplasmic reticulum membrane protein that can cluster near the cell membrane after calcium store depletion (UniProt Q13586). In paraffin sections, expect mainly cytoplasmic staining across many tissues, including high staining in esophageal squamous cells, kidney collecting ducts, and lung macrophages (HPA tissue IHC). HPA rates its tissue staining reliability Enhanced, with medium consistency between staining and RNA expression data (HPA tissue IHC).
| Cytoplasmic staining in esophageal squamous cells, kidney collecting ducts, or lung macrophages. | These are high-staining cell populations in HPA tissue IHC; compare intensity within the relevant cells, not across the entire section (HPA tissue IHC; general IHC practice). |
| Cytoplasmic or membrane-associated staining in cerebellar Purkinje cells. | Both compartments are reported for these cells; membrane-associated signal is also compatible with STIM1 topology (HPA: High in Purkinje cells; UniProt Q13586 topology). |
| Strong nuclear-only staining with little cytoplasmic signal. | This conflicts with the reported endoplasmic reticulum, cytoplasmic, and membrane locations; investigate staining artefact or antibody specificity (UniProt Q13586; HPA tissue IHC; general IHC practice). |
| Signal confined to cardiomyocytes or adipocytes, without staining in an included known-positive cell population. | HPA reports STIM1 as not detected in those cells. Check cell identification, nonspecific binding, and endogenous chromogenic activity before assigning the signal to STIM1 (HPA tissue IHC; general IHC practice). |
| Uniform stain over cells and surrounding tissue, obscuring cell boundaries. | Diffuse background cannot establish STIM1 localisation; assess blocking, detection reagents, and staining in a control lacking primary antibody (general IHC practice). |
💡Expected STIM1 appearanceA convincing positive shows predominantly cytoplasmic staining in an HPA high-staining population such as kidney collecting ducts, with cell boundaries discernible; nuclear-only or diffuse, cell-independent color is suspect (HPA tissue IHC; UniProt Q13586; general IHC practice).
| Tissue and cell choice | HPA reports variable cytoplasmic expression in most tissues. Use a named high-staining cell population to judge sensitivity; a low-staining population is a weaker benchmark (HPA tissue IHC). |
| Subcellular topology | STIM1 spans a membrane at residues 214–234, with residues 23–213 on the luminal or extracellular side and 235–685 cytoplasmic. Epitope location may matter, but the tested antibody's epitope is unspecified here (UniProt Q13586 topology). |
| Calcium-dependent distribution | Store depletion can move STIM1 into puncta at endoplasmic reticulum–plasma membrane junctions. A routine tissue section does not establish the calcium state or require visible puncta for a positive call (UniProt Q13586; general IHC practice). |
| Antibody evidence | HPA lists HPA011088 and HPA012123 as Enhanced for IHC, and CAB037128 and CAB037288 as Supported. These ratings support interpretation of HPA patterns; they do not validate an unspecified catalog antibody (HPA antibodies). |
| Low or undetected populations | HPA reports low staining in skeletal myocytes and ovarian stromal cells, and no detection in adipocytes or cardiomyocytes. Score the named cell type; other cells in those tissues can have different staining (HPA tissue IHC). |
| IF/ICC Q: What localisation is expected? | A: Predominantly endoplasmic reticulum signal is supported by HPA ICC-IF; UniProt also reports junctional puncta after calcium store depletion. The IF/ICC result does not prescribe an IHC-P workflow (HPA subcellular; UniProt Q13586). |
| Situation | Likely cause | Next action |
|---|---|---|
| No signal in esophageal squamous cells or kidney collecting ducts. | These cells are HPA high-staining; a failed run, inadequate detection, or antibody-specific performance is possible (HPA tissue IHC; general IHC practice). | Check the positive-control section, primary-antibody and detection steps, and the catalog antibody's IHC-P instructions; repeat with matched controls if needed (general IHC practice). |
| Signal appears only in nuclei. | Nuclear-only staining disagrees with reported STIM1 localisation (UniProt Q13586; HPA tissue IHC). | Review morphology and counterstain, then compare with a known-positive section and a control lacking primary antibody (general IHC practice). |
| Broad brown haze obscures cells. | Nonspecific reagent binding or chromogenic background may obscure the reported cytoplasmic pattern (HPA tissue IHC; general IHC practice). | Review blocking and detection steps; compare with a control lacking primary antibody before scoring (general IHC practice). |
| Strong signal is assigned to adipocytes or cardiomyocytes. | HPA reports STIM1 as not detected in those cell populations; cell misidentification, nonspecific staining, or endogenous detection activity may explain it (HPA tissue IHC; general IHC practice). | Confirm cell identity, inspect a control lacking primary antibody, and check endogenous enzyme blocking if using an enzyme-based detector (general IHC practice). |
| A low-staining tissue is scored as negative. | Weak signal can be difficult to distinguish from background; HPA reports low staining in hippocampal neuronal cells, ovarian stromal cells, and skeletal myocytes (HPA tissue IHC). | Judge the run against a named HPA high-staining cell population before interpreting a low-staining population (HPA tissue IHC; general IHC practice). |
| Expected calcium-dependent puncta are absent in a tissue section. | UniProt links junctional puncta to calcium store depletion; that state is not established by routine IHC appearance alone (UniProt Q13586; general IHC practice). | Use the reported cytoplasmic pattern and named positive cell populations for the IHC call; reserve puncta interpretation for an experiment that defines calcium state (HPA tissue IHC; UniProt Q13586). |
Experiment evidence
IHC & IF images showing STIM1 staining
A00312-1 · IHCIHC analysis of STIM1 using anti-STIM1 antibody (A00312-1). STIM1 was detected in a paraffin-embedded section of human breast cancer tissue.
A00312-1 · IHCIHC analysis of STIM1 using anti-STIM1 antibody (A00312-1). STIM1 was detected in a paraffin-embedded section of human breast cancer tissue.
A00312-1 · IFIF analysis of STIM1 using anti-STIM1 antibody (A00312-1). STIM1 was detected in a paraffin-embedded section of human placenta tissue. Heat
PB9406 · IHCIHC analysis of STIM1 using anti-STIM1 antibody (PB9406). STIM1 was detected in a paraffin-embedded section of mouse intestine tissue. Heat
PB9406 · IHCIHC analysis of STIM1 using anti-STIM1 antibody (PB9406). STIM1 was detected in a paraffin-embedded section of rat intestine tissue. Heat me
PB9406 · IFIF analysis of STIM1 using anti-STIM1 antibody (PB9406). STIM1 was detected in immunocytochemical section of A549 cells. Enzyme antigen retr
M00312-2 · IHCMouse spleen was stained with anti-Stromal Interaction Molecule 1 rabbit antibody
M00312-2 · IHCHuman breast was stained with anti-Stromal Interaction Molecule 1 rabbit antibody
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000167323-STIM1/tissue/cerebral+cortex#imid_3267068
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000167323-STIM1/tissue/colon#imid_3266994
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000167323-STIM1/tissue/liver#imid_3267003
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000167323-STIM1/tissue/kidney#imid_3266988
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA011088; green = STIM1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA011088; green = STIM1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for STIM1 IHC & IF
🧪Run lung first: macrophages should stain strongly (HPA: High in lung macrophages). Use adipose tissue as a negative, with adipocytes expected to lack detectable staining (HPA: Not detected in adipocytes); on the lung slide, treat neighboring unstained cells as provisional internal negatives only, since their STIM1 status is not specified by HPA.
Positive control tissue: Cerebellum (Purkinje cells - cytoplasm/membrane, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show STIM1 in A-431, U-251MG, A-549, U2OS, with annotated localisation: Endoplasmic reticulum (enhanced) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and a rabbit IgG isotype control matched to the primary antibody’s clonality (standard IHC practice; A00312-1 caption: rabbit primary). Use STIM1-knockout material as a biological specificity control, and quench endogenous peroxidase and assess macrophage pigment before interpreting lung DAB staining (standard IHC practice; HPA: High in lung macrophages).
⚠️Feasibility: No target-specific fixation window or fixation effect is reported in the supplied evidence, and the fixative is unreported in the selected A00312-1 tissue-IHC caption (A00312-1 caption: fixative not stated). The documented paraffin-section workflow uses heat-mediated EDTA retrieval at pH 8.0, so retrieval should be checked against a matched control section (A00312-1 caption: EDTA retrieval). The supplied evidence does not establish whether frozen sections or IF are easier for STIM1; macrophage pigment can complicate chromogenic scoring in lung (HPA: High in lung macrophages; standard IHC practice).
HPA tissue IHC evidence for STIM1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Cerebellum | Purkinje cells - cytoplasm/membrane | High | Protein (IHC) | HPA → |
| Endometrium | Glandular cells | Medium | Protein (IHC) | HPA → |
| Esophagus | Squamous epithelial cells | High | Protein (IHC) | HPA → |
| Kidney | Collecting ducts | High | Protein (IHC) | HPA → |
| Lung | Macrophages | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Caudate | Glial cells | Not detected | Protein (IHC) | HPA → |
| Heart muscle | Cardiomyocytes | Not detected | Protein (IHC) | HPA → |
| Smooth muscle | Smooth muscle cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced STIM1 IHC Tips
Troubleshoot STIM1 staining in paraffin sections by checking retrieval, compartment patterns, cell identity and assay controls.
What retrieval should I start with for weak STIM1 staining?
Start with heat-mediated retrieval in EDTA at pH 8.0 for paraffin sections (datasheet A00312-1). The selected tissue image used this retrieval before staining with 2 μg/ml antibody overnight at 4°C (datasheet A00312-1). If staining is weak, compare retrieval duration across adjacent sections while holding antibody concentration and DAB development time constant (standard IHC practice). Include a section with expected strong staining, such as lung macrophages, to distinguish failed retrieval from low expression in the study sample (HPA: High in lung macrophages; standard IHC practice). Check tissue preservation and section adhesion before increasing retrieval intensity, because damaged sections can make staining difficult to interpret (standard IHC practice).
Could fixation explain weak or uneven STIM1 staining?
The selected paraffin-section caption does not report its fixative, so target-specific fixation sensitivity is unknown for this antibody (datasheet A00312-1). Record fixative, fixation duration, section age and processing history before comparing cases; differences in those conditions can affect IHC staining generally (standard IHC practice). For a controlled comparison, process matched samples with the same routine fixation procedure and stain them together using EDTA at pH 8.0 (standard IHC practice; datasheet A00312-1). If staining differs, repeat with matched sections and an expected positive cell population before attributing the result to STIM1 biology (HPA: High in lung macrophages; standard IHC practice). Do not infer fixation sensitivity from STIM1 topology or tissue expression alone (UniProt Q13586 topology; HPA tissue IHC).
Is diffuse cytoplasmic STIM1 staining plausible in IHC?
Yes: variable cytoplasmic staining in most tissues is the reported tissue IHC pattern, while the endoplasmic reticulum is the enhanced subcellular location (HPA tissue IHC; HPA subcellular). STIM1 also occupies endoplasmic reticulum and cell membranes, with a cytoplasmic domain spanning residues 235–685 (UniProt Q13586 localisation and topology). After calcium-store depletion it can form puncta at endoplasmic reticulum–plasma membrane junctions, although routine chromogenic sections may not resolve those structures reliably (UniProt Q13586 localisation; standard IHC practice). Compare staining within the expected cell compartment and against neighboring cells under identical development conditions (standard IHC practice). Predominantly nuclear staining warrants scrutiny with controls because a nuclear location is absent from the supplied STIM1 localisation record (UniProt Q13586 localisation; standard IHC practice).
Can epitope position change how I interpret staining?
Yes: STIM1 has 2 recorded isoforms, but the supplied antibody caption does not identify its epitope or establish isoform coverage (UniProt Q13586 isoforms; datasheet A00312-1). The mature chain begins at residue 23, crosses the membrane at residues 214–234, and has a cytoplasmic region at residues 235–685 (UniProt Q13586 processing and topology). An antibody against the luminal region may respond differently to retrieval than one against the cytoplasmic region; that is a testable possibility, not a demonstrated effect for this antibody (UniProt Q13586 topology; standard IHC practice). Obtain the mapped epitope before making isoform-specific claims, then compare matched sections and controls under the same retrieval and detection conditions (standard IHC practice). Glycosylation sites at residues 131 and 171 likewise do not establish an effect on this antibody without epitope evidence (UniProt Q13586 glycosylation).
How should I investigate STIM1 localisation with multiplex IF?
Use IF as a separate assay and validate staining on the intended specimen; the selected antibody evidence describes chromogenic IHC in a paraffin section (datasheet A00312-1; standard IF practice). Multiplex STIM1 with a marker for an expected cell population, such as macrophages in lung, to check cell identity (HPA: High in lung macrophages; standard IF practice). Select a fluorophore in a channel with low measured tissue autofluorescence, and image single-stain and no-primary controls with identical settings (standard IF practice). STIM1 spans residues 214–234, so set permeabilisation according to whether the antibody recognises the luminal or cytoplasmic side; its epitope is unreported here (UniProt Q13586 topology; datasheet A00312-1). Evaluate any puncta alongside endoplasmic reticulum localisation rather than treating fluorescence intensity alone as evidence of translocation (UniProt Q13586 localisation; HPA subcellular; standard IF practice).
How can I reduce widespread brown background?
First examine a no-primary control processed with the same secondary reagent and DAB timing to identify detection-system background (standard IHC practice). The selected image used a peroxidase-conjugated secondary and DAB, so include a routine endogenous-peroxidase block when reproducing that chromogenic workflow (datasheet A00312-1; standard IHC practice). Its tissue section was blocked with 10% goat serum and incubated with 2 μg/ml primary antibody overnight at 4°C (datasheet A00312-1). If background persists, compare primary-antibody concentration, wash stringency and DAB development across matched sections while preserving a positive control (standard IHC practice). Interpret residual diffuse cytoplasmic staining cautiously because STIM1 can be expressed at variable levels in many tissues (HPA tissue IHC; standard IHC practice).
What is a defensible way to quantify STIM1 IHC? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and compartment before scoring, because tissue IHC reports variable cytoplasmic expression and cell-specific differences (HPA tissue IHC). For an ordinal readout, report the percentage of cells at each intensity and calculate an H-score as 1×(% weak) + 2×(% moderate) + 3×(% strong) (standard IHC practice). Alternatively, report percent positive cells or positive-cell density per mm² within a predefined tissue region (standard IHC practice). Normalize positive counts to the number of evaluable cells, or area-based counts to evaluable tissue area, and exclude necrosis and section edges consistently (standard IHC practice). Keep retrieval, illumination, DAB timing and scoring thresholds fixed across compared sections, with blinded review when feasible (standard IHC practice).
How do I distinguish true STIM1 staining from artefact?
Look for a reproducible cytoplasmic or membrane-associated pattern in expected cells, such as lung macrophages or kidney collecting ducts (HPA: High in lung macrophages and kidney collecting ducts; UniProt Q13586 localisation). Compare those cells with HPA-reported undetected populations, such as adipocytes, while recognizing that tissue context and assay conditions can differ (HPA: Not detected in adipocytes; standard IHC practice). Treat isolated nuclear staining, strong section-edge staining and staining confined to necrotic areas as possible artefacts requiring control review (UniProt Q13586 localisation; standard IHC practice). A no-primary control and a routine endogenous-peroxidase block help assess nonspecific chromogen deposition in this DAB workflow (datasheet A00312-1; standard IHC practice). Do not interpret a single DAB pattern as proof of calcium-store depletion or STIM1 translocation without an independent functional or localisation assay (UniProt Q13586 function and localisation; standard IHC practice).
Boster reagents
Best STIM1 / Stromal interaction molecule 1 IHC Antibodies
IHC and IF image captions document anti-STIM1 staining in human, mouse, and rat tissues, plus A549 cells for IF (catalog image captions).
Real IHC data
Anti-STIM1 Antibody ®
Cat # A00312-1
Real IHC data
Anti-STIM1 Antibody ®
Cat # PB9406
Real IHC data
Anti-Stromal Interaction Molecule 1 Rabbit Monoclonal Antibody
Cat # M00312-2
A00312-1 shows IHC in paraffin-embedded human breast cancer and IF in paraffin-embedded human placenta, mouse testis, and rat testis; PB9406 shows IHC in paraffin-embedded mouse intestine and IF in A549 cells (A00312-1 and PB9406 image captions). M00312-2 shows IHC in mouse spleen and lists IF as an application, but has no IF image (M00312-2 image captions; catalog applications).
Which to pick: For tissue IHC, choose A00312-1 for a human paraffin-section example at 2 μg/ml or PB9406 for a mouse intestine paraffin-section example at 1 μg/ml; both captions specify EDTA retrieval at pH 8.0, but neither reports the fixative (A00312-1 and PB9406 IHC image captions). For IF/ICC, PB9406 lists both applications and has an A549 IF image; A00312-1 has tissue IF images, while M00312-2 lists IF without an IF image (catalog applications; IF image captions). For cross-species IHC, PB9406 has paraffin-section images from human, mouse, and rat; recombinant rabbit monoclonal M00312-2 has human and mouse tissue IHC images and lists all three species, but its image captions do not report section processing or fixative (PB9406 IHC image captions; M00312-2 image captions; M00312-2 catalog description and reactivity).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q13586 (STIM1_HUMAN, Stromal interaction molecule 1).
- Human Protein Atlas. STIM1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. STIM1 subcellular location (ICC-IF): Localized to the endoplasmic reticulum..
- Human Protein Atlas. STIM1 antibody validation summary (4 antibodies).
- The purified extract of steamed Panax ginseng protects cardiomyocyte from ischemic injury via caveolin-1 phosphorylation-mediating calcium influx. Journal of ginseng research 2023 — PMC10721475.
- Expression of Orai1 and STIM1 in human oral squamous cell carcinogenesis. Journal of dental sciences 2022 — PMC8739746.
- Overexpression of stromal interaction molecule 1 may promote epithelial‑mesenchymal transition and indicate poor prognosis in gastric cancer. Molecular medicine reports 2017 — PMC5482137.
- STIM1/SOX2 proteins are co-expressed in the tumor and microenvironmental stromal cells of pancreatic ductal adenocarcinoma and ampullary carcinoma. World journal of surgical oncology 2024 — PMC10964627.
- PubMed PMID:8921403 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
- PubMed PMID:16554811 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for STIM1 (Stromal interaction molecule 1). Expected localisation Variable cytoplasmic staining (HPA tissue IHC); ER and cell membrane localization (UniProt). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A00312-1). Validated IHC antibody: A00312-1 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Cerebellum (Purkinje cells - cytoplasm/membrane); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human breast cancer tissue; fixative not specified (datasheet A00312-1); 2. Fixation: Image fixative and duration unreported (datasheet A00312-1); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat retrieval: EDTA pH 8.0 (datasheet A00312-1); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A00312-1); 8. Primary antibody: Rabbit anti-STIM1, 2-5 μg/ml (datasheet A00312-1); 9. Primary incubation: Overnight at 4 °C (datasheet A00312-1). Watch for: Fixation: Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific); Caveat: Calcium-store depletion can shift STIM1 to ER–membrane junctions (UniProt); Isoform / epitope: 2 isoforms; map the epitope to the extracellular or cytoplasmic region (UniProt); Regulation: Intensity varies by cell type (HPA tissue IHC). Evidence: UniProt Q13586, HPA tissue IHC · Enhanced, HPA ICC-IF · endoplasmic reticulum., Datasheet A00312-1, PMC8739746, PMC10964627. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/STIM1/immunohistochemistry-ihc-guide.