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IQGAP1 / Ras GTPase-activating-like protein IQGAP1 · IHC design guide
Design Immunohistochemistry for IQGAP1
Plan chromogenic IQGAP1 IHC on paraffin sections using an IHC-validated antibody (datasheet A01603). Assess cytoplasmic and membranous staining by cell type, using high staining in colon glandular cells and undetected staining in adipocytes as reference patterns (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
IQGAP1 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 | Cytoplasmic and membranous in most cell types (HPA tissue IHC) | |
| Staining pattern | Most cell types show cytoplasmic and membrane staining (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet A01603) | |
| Positive control | Colon+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep paraffin-section fixation consistent across samples. (standard IHC practice; not target-specific) | |
| Caveat | Adipocytes may lack staining despite widespread expression (HPA tissue IHC) | |
| Regulation | Nuclear levels rise at G1/S (UniProt) | |
| Isoform / epitope | No annotated isoforms; chain spans residues 2–1657 (UniProt) |
Section 1
Recommended IQGAP1 IHC & IF Protocols
The catalog antibody protocol uses citrate pH 6 retrieval (datasheet A01603). These four published IHC protocols provide tissue specific examples (PMC5406000; PMC5588162; PMC9628040; PMC4249885).
| Sample | Paraffin-embedded human intestinal cancer tissue; fixative not specified (datasheet A01603) |
| Fixation | Image fixative and duration unreported (datasheet A01603); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: Citrate pH 6, 20 min (datasheet A01603) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A01603) |
| Primary antibody | Rabbit anti-IQGAP1, 0.5-1μg/ml (datasheet A01603) |
| Primary incubation | Overnight at 4 °C (datasheet A01603) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A01603) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | IQGAP1-positive staining in glandular cells of colon (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic and membranous expression in most cell types. No signal in the no-primary control. |
💡Decision noteTry heat-mediated citrate pH 6 retrieval first (datasheet A01603); three published protocols also use citrate pH 6 (PMC5588162; PMC9628040; PMC4249885).
Section 2
What Is the Expected IQGAP1 Staining Pattern?
IQGAP1 should show predominantly cytoplasmic and membranous staining in many cell types (HPA: tissue IHC profile, Enhanced reliability). High staining is reported in colon and endometrial glandular cells, kidney glomerular cells, lung macrophages, and placental trophoblastic cells (HPA: High). Cell cortex, apical and basolateral membranes, cytoplasm, and nucleus are listed locations; IQGAP1 has no transmembrane segment (UniProt P46940: subcellular location and topology).
| Cytoplasmic staining with a membrane or cortical accent in the expected cells. | This fits the broad tissue IHC pattern (HPA: cytoplasmic and membranous expression in most cell types) and the listed cell cortex and membrane locations (UniProt P46940: subcellular location). Judge intensity against the cell type, rather than expecting every cell in a section to match. |
| Predominantly extracellular staining, or a compartment pattern that obscures the expected cellular signal. | Extracellular staining is discordant with the reported cellular locations (UniProt P46940: subcellular location). Check morphology and detection controls before calling it target signal (general IHC practice). Nuclear staining alone needs context: nuclear IQGAP1 is reported, with levels increasing at G1/S (UniProt P46940: cell-cycle distribution). |
| Strong staining in adipocytes or skeletal myocytes while an expected positive cell population is visible. | Those cell populations are listed as not detected in the sampled HPA tissue IHC images (HPA: adipocytes and skeletal myocytes, Not detected). Suspect cross-reactivity or endogenous detection activity and investigate with controls (general IHC practice); one discordant section cannot establish which cause applies. |
| A diffuse chromogenic haze covers cells and surrounding tissue, with little compartment detail. | The haze does not resolve the expected cytoplasmic and membranous pattern (HPA: tissue IHC profile). Evaluate background with a no-primary control, blocking and wash steps, and the detection system (general IHC practice) before scoring weak staining as IQGAP1. |
| No staining in a section containing an expected high-staining cell population. | First confirm that the relevant cells are present: HPA reports High staining in colon glandular cells, kidney glomerular cells, and lung macrophages, among others (HPA: tissue IHC). If they are present, inspect the paraffin IHC workflow and detection controls (general IHC practice). |
💡Expected IQGAP1 appearanceCall positive when identifiable cells show cytoplasmic staining with membranous or cortical accent, especially in HPA High populations (HPA: tissue IHC; UniProt P46940: subcellular location); diffuse extracellular color or staining limited to HPA Not detected cells warrants investigation before scoring (HPA: tissue IHC; general IHC practice).
| Cell type and tissue | HPA reports High staining in several distinct populations, including placental trophoblastic cells and spleen red-pulp cells, but Not detected staining in adipocytes and skeletal myocytes (HPA: tissue IHC). Use the identified cell population when interpreting a mixed tissue; tissue name alone is insufficient. |
| Cell-cycle distribution | Nuclear IQGAP1 is a listed location, and nuclear levels increase at G1/S (UniProt P46940: subcellular location). A nuclear component is therefore plausible; a single IHC section cannot assign cell-cycle phase from IQGAP1 staining alone (general IHC interpretation). |
| Membrane topology | IQGAP1 has no transmembrane segment, despite its reported membrane and cell-cortex locations (UniProt P46940: topology and subcellular location). A membrane accent can fit the record; it should not be interpreted as evidence that IQGAP1 spans the membrane. |
| Antibody evidence | The tissue IHC profile has Enhanced reliability, described as high consistency between antibody staining and RNA expression data (HPA: tissue IHC reliability). HPA014055 and CAB013302 each have Enhanced IHC status (HPA: antibody validation). These summaries support pattern selection, not every individual slide. |
| IF/ICC Q: What pattern should I expect? | A: Plasma membrane and cell-junction localization is supported in the HPA ICC-IF summary (HPA: subcellular ICC-IF). Interpret that observation within IF/ICC; the paraffin chromogenic IHC expectation comes from the HPA tissue IHC profile (HPA: tissue IHC). |
| Situation | Likely cause | Next action |
|---|---|---|
| The expected positive cells are present, but the IHC slide is blank. | A missed primary-antibody or detection step, or insufficient retrieval, can leave paraffin IHC without visible signal (general IHC practice). | Check the primary and detection sequence, compare a known positive section, and review the retrieval conditions used for this assay (general IHC practice; HPA: High cell populations identify candidate positive controls). |
| Color is strongest outside cells or in damaged areas. | That distribution does not match the listed cellular locations (UniProt P46940: subcellular location); tissue damage or nonspecific deposition may contribute (general IHC practice). | Compare intact morphology with a no-primary control and inspect washes and chromogen development (general IHC practice). Score only signal assigned to identifiable cells. |
| Nearly every nucleus is dark, with little cytoplasmic or membrane signal. | Nuclear IQGAP1 is possible, but a nucleus-only field departs from the broad tissue IHC profile (UniProt P46940: nucleus and G1/S regulation; HPA: cytoplasmic and membranous profile). | Check nuclear counterstain intensity and no-primary control, then reassess whether the dark signal belongs to chromogen or counterstain (general IHC practice). |
| Adipocytes stain strongly while expected positive cells are weak. | Adipocytes are Not detected in the HPA tissue record (HPA: adipose tissue IHC). Off-target staining or endogenous detection activity is possible (general IHC practice). | Run a no-primary control and inspect background in the same tissue; compare signal in an HPA High cell population before assigning specificity (general IHC practice; HPA: tissue IHC). |
| A faint, even haze makes weak cells appear positive. | Background obscures the reported cytoplasmic and membranous distribution (HPA: tissue IHC profile); its source cannot be inferred from appearance alone (general IHC practice). | Use a no-primary control, review blocking and washing, and score only signal with clear cell and compartment boundaries (general IHC practice). |
| The no-primary control also develops chromogenic color. | The color cannot be attributed solely to primary-antibody binding; endogenous activity or detection-system background may contribute (general IHC practice). | Review the chromogenic detection controls and endogenous-activity blocking appropriate to the detection system, then repeat the comparison (general IHC practice). |
Experiment evidence
IHC & IF images showing IQGAP1 staining
A01603 · IHCIHC analysis of IQGAP1 using anti-IQGAP1 antibody (A01603). IQGAP1 was detected in paraffin-embedded section of human intestinal cancer tiss
A01603 · IHCIHC analysis of IQGAP1 using anti-IQGAP1 antibody (A01603). IQGAP1 was detected in paraffin-embedded section of human intestinal cancer tiss
A01603 · IFIF analysis of IQGAP1 using anti-IQGAP1 antibody (A01603). IQGAP1 was detected in immunocytochemical section of U20S cells. Enzyme antigen r
A01603-1 · IHCIHC analysis of IQGAP1 using anti-IQGAP1 antibody (A01603-1). IQGAP1 was detected in a paraffin-embedded section of human endometrial adenoc
A01603-1 · IHCIHC analysis of IQGAP1 using anti-IQGAP1 antibody (A01603-1). IQGAP1 was detected in a paraffin-embedded section of human ovarian cancer tis
A01603-1 · IFIF analysis of IQGAP1 using anti-IQGAP1 antibody (A01603-1). IQGAP1 was detected in immunocytochemical section of A431 cells. Enzyme antigen
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000140575-IQGAP1/tissue/cerebral+cortex#imid_3677080
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000140575-IQGAP1/tissue/colon#imid_3676990
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000140575-IQGAP1/tissue/liver#imid_3677007
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000140575-IQGAP1/tissue/kidney#imid_3677000
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB013302; green = IQGAP1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB013302; green = IQGAP1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for IQGAP1 IHC & IF
🧪Run colon first; its glandular cells should stain (HPA: High in colon glandular cells). Use adipose tissue adipocytes as a negative comparator (HPA: Not detected in adipocytes); on the colon slide, internal negative cells should show only background staining, without assuming that every nonglandular cell is negative.
Positive control tissue: Colon (Glandular cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show IQGAP1 in A-431, U-251MG, U2OS, with annotated localisation: Plasma membrane (supported), Cell Junctions (supported) (HPA subcellular).
Technical controls: Include a no-primary (secondary-only) slide, a concentration-matched rabbit IgG isotype control (selected-SKU caption: rabbit primary antibody), and an IQGAP1-knockout biological control if available. For colon sections, check endogenous peroxidase and biotin background because the selected-SKU caption uses biotin-based detection with DAB (selected-SKU caption: SABC and DAB).
⚠️Feasibility: No target-specific fixation window or fixation effect is reported in the supplied evidence, and the selected-SKU tissue-IHC caption does not state a fixative (selected-SKU caption: fixative unreported). The reported paraffin-section procedure uses citrate retrieval at pH 6 for 20 minutes; its dependence on retrieval has not been established (selected-SKU caption: citrate retrieval). The supplied evidence does not establish whether frozen sections or IF are easier; for the reported colon method, assess endogenous biotin and peroxidase as potential detection artefacts (selected-SKU caption: SABC and DAB).
HPA tissue IHC evidence for IQGAP1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High 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 |
|---|---|---|---|---|
| Colon | Glandular cells | High | Protein (IHC) | HPA → |
| Endometrium | Glandular cells | High | Protein (IHC) | HPA → |
| Kidney | Cells in glomeruli | High | Protein (IHC) | HPA → |
| Lung | Macrophages | High | Protein (IHC) | HPA → |
| Lymph node | Non-germinal center cells | 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 → |
| Cerebellum | Cells in granular layer | Not detected | Protein (IHC) | HPA → |
| Hippocampus | Glial cells | Not detected | Protein (IHC) | HPA → |
| Skeletal muscle | Myocytes | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced IQGAP1 IHC Tips
Use the catalog antibody’s paraffin section workflow as the starting point, then judge IQGAP1 staining by cell type, compartment, and matched controls.
How should I troubleshoot weak IQGAP1 staining after antigen retrieval?
Start with heat-mediated retrieval in citrate buffer at pH 6 (datasheet A01603). The catalog antibody’s paraffin section image used 20 minutes of retrieval, followed by 1 μg/ml primary antibody overnight at 4°C (caption A01603). If staining is weak, confirm that sections stayed covered by retrieval solution and compare a shorter and longer heating interval on adjacent sections (standard IHC practice). Use colon glandular cells or placental trophoblastic cells as a positive reference when available (HPA: High in those cells). Judge any improvement against tissue damage and background, since stronger DAB alone does not establish specific IQGAP1 staining (standard IHC practice).
Could fixation explain absent or patchy IQGAP1 staining?
The selected paraffin section caption does not report a fixative, so target-specific fixation sensitivity is unknown (caption A01603). Record the specimen’s fixative, fixation duration, processing history, and section age before comparing staining across cases (standard IHC practice). Run adjacent sections through the same citrate pH 6 retrieval and 20-minute heating used for the catalog image (caption A01603). Include a known positive compartment, such as colon glandular cells, to check whether the staining run worked (HPA: High in colon glandular cells). If fixation histories differ, interpret intensity differences cautiously and compare matched specimens processed together (standard IHC practice).
Is nuclear IQGAP1 staining plausible when membrane staining dominates?
Cytoplasmic and membranous staining in most cell types is the expected tissue pattern (HPA: tissue IHC profile). Plasma membrane and cell junction localization also have support from cell imaging (HPA: subcellular summary). Nuclear localization is reported, with nuclear levels increasing at G1/S, so a nuclear signal is biologically plausible in a subset of cells (UniProt P46940: subcellular localization). Compare nuclear DAB with the cell borders and cytoplasm on a hematoxylin-counterstained section, using the same exposure and development conditions across specimens (standard IHC practice). Confirm an unexpected nuclear-only pattern with an independently validated antibody or orthogonal assay before assigning biological meaning (standard IHC practice).
How can I assess whether an unusual staining pattern reflects epitope behavior?
The supplied record lists 0 annotated isoforms and gives no binding epitope for A01603, so an isoform-specific staining claim is unsupported (UniProt P46940: isoforms; caption A01603). IQGAP1 contains a calponin-homology region at residues 44–159 and a Ras-GAP region at 1020–1269 (UniProt P46940: domains). Reported modifications include phosphotyrosine at 172 and PKC-linked phosphoserine at 1441, but their effect on this antibody is unknown (UniProt P46940: modified residues). Compare adjacent sections under the same citrate pH 6 retrieval conditions before attributing signal shifts to epitope accessibility (datasheet A01603; standard IHC practice). Seek epitope mapping or an independent antibody before interpreting compartment differences as distinct molecular forms (standard IHC practice).
How should I check an IQGAP1 IHC pattern with multiplex IF?
Use IF as a separate validation experiment alongside the chromogenic paraffin section result; the supplied A01603 caption documents IHC, not an IF protocol (caption A01603). Pair IQGAP1 with a marker identifying the expected cell population, such as a macrophage marker when examining lung macrophages (HPA: High in lung macrophages; standard IF practice). Choose a far-red fluorophore where tissue autofluorescence obscures shorter wavelengths, and inspect single-channel controls before judging overlap (standard IF practice). Because IQGAP1 has no transmembrane segment and can occupy cytoplasm and cortex, permeabilize when the antibody must reach an intracellular epitope; its exact epitope is unreported (UniProt P46940: topology and localization; standard IF practice). Compare the resulting cell borders and compartments with the IHC pattern, while keeping fluorescence and DAB intensity scores separate (standard IHC/IF practice).
What should I change when IQGAP1 DAB staining is diffuse?
First check whether the diffuse signal extends beyond the expected cytoplasmic and membranous compartments (HPA: tissue IHC profile). The catalog image used 10% goat serum blocking, 1 μg/ml primary antibody overnight at 4°C, and biotin-based DAB detection (caption A01603). Compare a no-primary control and a shorter DAB development on adjacent sections to identify detection background (standard IHC practice). Apply a peroxidase block for chromogenic detection and assess endogenous biotin if the biotin-based system produces widespread staining (standard IHC practice; caption A01603: detection system). Keep washing and counterstaining consistent while changing one variable at a time (standard IHC practice).
How should I score IQGAP1 staining across tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and compartment before scoring, since IQGAP1 can appear at membranes, in cytoplasm, and sometimes in nuclei (HPA: tissue IHC profile; UniProt P46940: subcellular localization). For a cellular readout, report percent positive cells and an H-score from 0–300, recording membrane, cytoplasmic, and nuclear scores separately (standard IHC practice). For spatially restricted populations, report positive cell density per mm² of viable, annotated tissue (standard IHC practice). Normalize counts to the relevant cell population or viable tissue area, and use identical threshold and DAB development settings across slides (standard IHC practice). Exclude folds, edges, and necrotic areas from the scored region (standard IHC practice).
How do I distinguish true IQGAP1 signal from artefact?
A convincing result follows recognizable cell boundaries or cytoplasm and occurs in an expected population, such as colon glandular cells or lung macrophages (HPA: tissue IHC profile; HPA: High in those cells). Treat staining confined to cut edges, folds, or necrotic areas as suspect and inspect the corresponding hematoxylin morphology (standard IHC practice). Compare a no-primary control to identify endogenous enzyme or detection-system color, particularly when using the caption’s biotin-based DAB method (standard IHC practice; caption A01603). Nuclear staining can be plausible because IQGAP1 nuclear levels rise at G1/S, but an isolated nuclear-only pattern warrants independent confirmation (UniProt P46940: subcellular localization; standard IHC practice). A negative adipocyte population can help assess contrast within a suitable section (HPA: Not detected in adipocytes).
Boster reagents
Best IQGAP1 / Ras GTPase-activating-like protein IQGAP1 IHC Antibodies
Two anti-IQGAP1 antibodies have paraffin-section IHC and cell-based IF figures (catalog image captions); A01603 lists human, mouse, and rat reactivity, while A01603-1 lists human reactivity (catalog reactivity).
Real IHC data
Anti-IQGAP1 Antibody ®
Cat # A01603
Real IHC data
Anti-IQGAP1 Antibody ®
Cat # A01603-1
A01603 will render with IHC data from human intestinal cancer tissue; its additional captions show human mammary cancer IHC and U20S cell IF (A01603 image captions). A01603-1 will render with IHC data from human endometrial adenocarcinoma; its additional captions show ovarian cancer and gallbladder squamous cell carcinoma IHC and A431 cell IF (A01603-1 image captions).
Which to pick: For paraffin-section IHC, A01603 uses citrate pH 6 retrieval for 20 min (A01603 IHC caption), while A01603-1 uses EDTA pH 8 retrieval (A01603-1 IHC caption); neither caption reports the fixative (respective IHC captions). For IF/ICC, A01603 has a U20S cell figure at 2 μg/ml (A01603 IF caption), and A01603-1 has an A431 cell figure at 5 μg/ml (A01603-1 IF caption). For mouse or rat samples, select A01603 based on its listed reactivity (catalog reactivity); clonality is unreported for both antibodies (catalog clone fields).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P46940 (IQGA1_HUMAN, Ras GTPase-activating-like protein IQGAP1).
- Human Protein Atlas. IQGAP1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. IQGAP1 subcellular location (ICC-IF): Localized to the plasma membrane and cell junctions..
- Human Protein Atlas. IQGAP1 antibody validation summary (2 antibodies).
- IQGAP1 is an oncogenic target in canine melanoma. PloS one 2017 — PMC5406000.
- Alterations in IQGAP1 expression and localization in colorectal carcinoma and liver metastases following oxaliplatin-based chemotherapy. Oncology letters 2017 — PMC5588162.
- Comprehensive analysis of the expression and prognosis for IQ motif-containing GTPase-activating proteins in hepatocellular carcinoma. BMC cancer 2022 — PMC9628040.
- Coexpression of IQ-domain GTPase-activating protein 1 (IQGAP1) and Dishevelled (Dvl) is correlated with poor prognosis in non-small cell lung cancer. PloS one 2014 — PMC4249885.
- PubMed PMID:8051149 — UniProt-cited evidence.
- PubMed PMID:7584044 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for IQGAP1 (Ras GTPase-activating-like protein IQGAP1). Expected localisation Cytoplasmic and membranous in most cell types (HPA tissue IHC). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet A01603). Validated IHC antibody: A01603 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Colon (Glandular cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human intestinal cancer tissue; fixative not specified (datasheet A01603); 2. Fixation: Image fixative and duration unreported (datasheet A01603); 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: Citrate pH 6 , 20 min (datasheet A01603); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A01603); 8. Primary antibody: Rabbit anti-IQGAP1, 0.5-1μg/ml (datasheet A01603); 9. Primary incubation: Overnight at 4 °C (datasheet A01603). Watch for: Fixation: Keep paraffin-section fixation consistent across samples. (standard IHC practice; not target-specific); Caveat: Adipocytes may lack staining despite widespread expression (HPA tissue IHC); Isoform / epitope: No annotated isoforms; chain spans residues 2–1657 (UniProt); Regulation: Nuclear levels rise at G1/S (UniProt). Evidence: UniProt P46940, HPA tissue IHC · Enhanced, HPA ICC-IF · plasma membrane and cell junctions., Datasheet A01603, PMC5406000, PMC5588162. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/IQGAP1/immunohistochemistry-ihc-guide.