PAK5 / Serine/threonine-protein kinase PAK 5 · IHC design guide

Design Immunohistochemistry for PAK5

Plan chromogenic PAK5 IHC on paraffin sections using cerebellum and cerebral cortex as high-staining references (HPA tissue IHC). This guide covers fixation consistency, interpretation of cytoplasmic CNS staining, and observed off-target binding (HPA tissue IHC).

Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use

Immunohistochemistry protocol sheet for PAK5 (IHC for PAK5): expected localisation Cytoplasmic staining in CNS (HPA tissue IHC), antibody PB9733, validated IHC image, and IHC protocol steps — Printable **PAK5** IHC protocol sheet — expected localisation Cytoplasmic staining in CNS (HPA tissue IHC), antibody PB9733, controls and protocol steps. Open the full PAK5 IHC guide →

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PAK5 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 staining in CNS (HPA tissue IHC)
	Staining pattern	Neuronal cytoplasmic staining in CNS (HPA tissue IHC)
	Antigen retrieval	EDTA pH 8.0 HIER, heat-mediated (datasheet PB9733)
	Positive control ⓘ	Cerebellum+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 fixation consistent across sections (standard IHC practice; not target-specific)
	Caveat	Presumed off-target binding was observed (HPA tissue IHC)
	Regulation	Expression regulation unreported (UniProt)
	Isoform / epitope	No alternative isoforms listed; one 1–719 chain (UniProt)

Section 1

Recommended PAK5 IHC & IF Protocols

The catalog antibody protocol uses EDTA pH 8.0 retrieval (datasheet: PB9733). The published PAK5 IHC methods below cover osteosarcoma, tissue microarrays, paraffin-embedded tissues, and lung sections (PMCs below).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Paraffin-embedded human glioma tissue; fixative not specified (datasheet PB9733)
Fixation	Image fixative and duration unreported (datasheet PB9733); 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 PB9733); 20 min, 95–100 °C (standard)
Peroxidase block	3% H2O2, 10 min, room temperature (standard)
Blocking	10% goat serum (datasheet PB9733)
Primary antibody	Rabbit anti-PAK5, 0.5-1μg/ml (datasheet PB9733)
Primary incubation	Overnight at 4 °C (datasheet PB9733)
Detection	Streptavidin-biotin complex (SABC), DAB chromogen (datasheet PB9733)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	PAK5-positive staining in gLUC cells - cytoplasm/membrane of cerebellum (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in CNS. No signal in the no-primary control.

💡Decision noteStart with EDTA pH 8.0 heat retrieval for the catalog antibody (datasheet: PB9733); citrate pH 6.0 was reported with a different PAK5 antibody (PMC5645986).

Section 2

What Is the Expected PAK5 Staining Pattern?

In paraffin-section IHC, expect predominantly cytoplasmic staining in CNS cells, especially neurons in cerebral cortex and hippocampus (HPA tissue IHC: Approved; cytoplasmic expression in CNS; High neuronal staining). PAK5 is also reported in mitochondria and nuclei, and has no transmembrane segment (UniProt Q9P286: subcellular location and topology). HPA notes that presumed off-target binding was observed and disregarded (HPA tissue IHC: reliability description).

What am I looking at on my slide?
Cytoplasmic staining is strong in cerebral cortex or hippocampal neurons, with a comparatively quiet negative-control section.	This matches the reported high neuronal staining and cytoplasmic CNS profile (HPA tissue IHC: cerebral cortex and hippocampus High; cytoplasmic expression in CNS). Score the relevant cells and compartment, rather than calling a section positive from its overall color.
Signal appears exclusively along cell borders, outside cells, or in another unexpected compartment.	Reassess specificity and detection before assigning it to PAK5: the reported IHC profile is cytoplasmic (HPA tissue IHC). Nuclear or mitochondrial staining alone cannot be dismissed categorically because those locations are reported for PAK5 (UniProt Q9P286: subcellular location).
Strong staining occurs in cells expected to be negative, such as bronchial respiratory epithelium.	The cell type conflicts with its reported 'Not detected' result (HPA tissue IHC: bronchus, respiratory epithelial cells). Consider antibody cross-reactivity or endogenous detection activity; HPA also records presumed off-target binding (HPA tissue IHC: reliability description). Compare the suspect cells with a matched detection control.
Color spreads across tissue and blank areas, obscuring cell boundaries and compartments.	Treat this as background until controls establish specific staining. Uneven blocking, residual detection activity, or excess detection reagent can produce diffuse chromogenic signal (standard IHC practice). The HPA tissue pattern does not establish a PAK5-specific cause for background (HPA tissue IHC: cytoplasmic CNS profile).
A cerebral cortex or hippocampus section shows no convincing neuronal staining.	These are reported high-staining neuronal examples (HPA tissue IHC: cerebral cortex and hippocampus). Check tissue preservation, retrieval, antibody and detection steps against the validated IHC procedure (standard IHC practice). A failed positive control makes a negative result elsewhere uninterpretable.

💡Expected PAK5 appearanceCall the IHC result positive when neuronal cytoplasm in cerebral cortex or hippocampus shows strong, cell-associated signal (HPA tissue IHC: High neuronal staining; cytoplasmic CNS profile); similarly strong signal in reportedly negative bronchial respiratory epithelium warrants a false-positive check (HPA tissue IHC: bronchus Not detected).

How each factor affects the staining
Tissue and cell selection	Cerebellar GLUC cells show high cytoplasm/membrane staining; cortex and hippocampal neurons show high staining, while caudate neurons show medium staining (HPA tissue IHC). Use the named cell populations when comparing sections.
Antibody evidence	The listed IHC-tested antibody HPA020444 is Approved; HPA071060 has no listed IHC status (HPA antibodies). Approved should not be read as IHC Enhanced, and presumed off-target binding was observed and disregarded (HPA tissue IHC: reliability description).
Subcellular interpretation	PAK5 has no transmembrane segment and is reported in cytoplasm, mitochondria and nucleus (UniProt Q9P286: topology and location). Cell-border staining requires context: cerebellar GLUC cells have reported cytoplasm/membrane staining (HPA tissue IHC).
IF/ICC Q&A: Where should signal appear?	HPA reports mainly supported nucleoplasmic staining, with supported nuclear membrane, cytosol and mitochondrial locations in ICC-IF (HPA subcellular). This is an IF observation; assess paraffin IHC against its cytoplasmic CNS profile (HPA tissue IHC).

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
Positive-control neurons are unstained.	The staining run may have failed; cortex and hippocampal neurons are reported High (HPA tissue IHC).	Review retrieval, primary-antibody application and chromogenic detection against the IHC-validated procedure, then repeat with a positive control (standard IHC practice). No PAK5-specific retrieval condition is supplied.
Suspect staining appears in bronchial respiratory epithelial cells.	These cells are reported Not detected (HPA tissue IHC: bronchus); off-target binding or endogenous detection activity is possible (HPA tissue IHC: reliability description; standard IHC practice).	Compare matched sections with the primary antibody omitted and inspect whether signal persists through detection (standard IHC practice). Interpret any remaining primary-dependent staining cautiously.
Diffuse brown color obscures neuronal cytoplasm.	Background may arise from blocking or detection steps (standard IHC practice); its cause cannot be assigned from the reported tissue pattern (HPA tissue IHC).	Check reagent exposure, washes and the no-primary control, then adjust the general staining workflow as indicated by those controls (standard IHC practice).
Signal is confined to extracellular spaces or unrelated tissue structures.	That distribution does not fit the reported cytoplasmic CNS IHC pattern (HPA tissue IHC) or PAK5's reported intracellular locations (UniProt Q9P286: subcellular location).	Inspect morphology and matched controls; do not score those structures as PAK5-positive without independent support (standard IHC interpretation).
A section looks negative despite visible stain elsewhere on the slide.	The stained cells may not be the expected population: HPA reports distinct cell-specific levels, including High in cortex neurons and Not detected in adipocytes (HPA tissue IHC).	Identify and score the specified cells separately, confirm that the positive-control neurons stained, and record the compartment and intensity for each population (standard IHC practice).
Nuclear signal seems at odds with the cytoplasmic IHC reference.	The methods have different reported emphasis: cytoplasmic CNS tissue staining in IHC (HPA tissue IHC), and mainly nucleoplasmic localization in ICC-IF (HPA subcellular).	Record nuclear and cytoplasmic signal separately. Check whether neuronal cytoplasmic staining and controls support the IHC result; do not infer an IHC protocol or expected intensity from ICC-IF images.

Source: UniProt Q9P286 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing PAK5 staining

IHC analysis of PAK5 using anti-PAK5 antibody (PB9733). PAK5 was detected in a paraffin-embedded section of human glioma tissue. Heat mediated antigen retrieval was performed in EDTA buffer (pH 8.0, epitope retrieval solution). The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 1 μg/ml rabbit anti-PAK5 Antibody (PB9733) overnight at 4°C. Biotinylated goat anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using Strepavidin-Biotin-Complex (SABC) (Catalog # SA1022) with DAB as the chromogen.

PB9733 · IHCIHC analysis of PAK5 using anti-PAK5 antibody (PB9733). PAK5 was detected in a paraffin-embedded section of human glioma tissue. Heat mediat

IHC analysis of PAK5/PAK7 using anti-PAK5/PAK7 antibody (PB9733). PAK5/PAK7 was detected in a paraffin-embedded section of human cerebellum tissue. Heat mediated antigen retrieval was performed in EDTA buffer (pH 8.0, epitope retrieval solution). The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 2 μg/ml rabbit anti-PAK5/PAK7 Antibody (PB9733) overnight at 4°C. Peroxidase Conjugated Goat Anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using HRP Conjugated Rabbit IgG Super Vision Assay Kit (Catalog # SV0002) with DAB as the chromogen.

PB9733 · IHCIHC analysis of PAK5/PAK7 using anti-PAK5/PAK7 antibody (PB9733). PAK5/PAK7 was detected in a paraffin-embedded section of human cerebellum

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000101349-PAK5/tissue/cerebral+cortex#imid_5510392

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000101349-PAK5/tissue/colon#imid_5510302

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000101349-PAK5/tissue/liver#imid_5510303

HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000101349-PAK5/tissue/kidney#imid_5510312

HPA · ICC-IF SH-SY5YHuman Protein Atlas immunofluorescence, SH-SY5Y, antibody HPA020444; green = PAK5, blue = nucleus, red = microtubules.

← swipe / scroll for more images →

Real IHC / IF data behind the staining-pattern expectations in this section.

Sample controls for PAK5 IHC & IF

🧪Run cerebral cortex first: neuronal cells should stain (HPA: High in cerebral cortex neuronal cells). Use bronchus respiratory epithelium as the negative tissue (HPA: Not detected); on the cortex slide, compare non-neuronal cells with the stained neurons as an internal background check, without assuming those cells are PAK5-negative.

Positive control tissue: Cerebellum (GLUC 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 PAK5 in SH-SY5Y, U-251MG, U2OS, HAP1, with annotated localisation: Nucleoplasm (supported) (HPA subcellular).

Technical controls: Include no-primary (secondary-only) and matched rabbit IgG isotype controls (selected PB9733 caption: rabbit primary antibody), plus PAK5-knockout material as a biological specificity control if available. Quench endogenous peroxidase for chromogenic IHC and assess neuronal lipofuscin autofluorescence if using IF (standard IHC/IF practice).

⚠️Feasibility: No target-specific fixation window or fixation effect is reported in the supplied evidence; the selected PB9733 paraffin-section caption does not state a fixative. Paraffin IHC has a documented starting condition of heat retrieval in EDTA at pH 8.0 (selected PB9733 tissue-IHC caption); frozen-section feasibility is unreported, while IF/ICC localization images are available (HPA subcellular). Brain lipofuscin can complicate interpretation, especially in IF (standard IHC/IF practice).

HPA tissue IHC evidence for PAK5

Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Presumed off target binding observed and disregarded.). 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	GLUC cells - cytoplasm/membrane	High	Protein (IHC)	HPA →
Cerebral cortex	Neuronal cells	High	Protein (IHC)	HPA →
Hippocampus	Neuronal cells	High	Protein (IHC)	HPA →
Testis	Spermatogonia cells	High	Protein (IHC)	HPA →
Caudate	Neuronal cells	Medium	Protein (IHC)	HPA →

Undetected expression · recommended negative controls

Tissue	Cell type	Level	Evidence	Source
Adipose tissue	Adipocytes	Not detected	Protein (IHC)	HPA →
Adrenal gland	Glandular cells	Not detected	Protein (IHC)	HPA →
Appendix	Glandular cells	Not detected	Protein (IHC)	HPA →
Breast	Adipocytes	Not detected	Protein (IHC)	HPA →
Bronchus	Respiratory epithelial cells	Not detected	Protein (IHC)	HPA →

Section 3

Advanced PAK5 IHC Tips

Troubleshoot PAK5 staining in paraffin sections by checking retrieval, cellular location, controls and scoring before interpreting chromogenic signal.

What should I change when PAK5 staining is weak after antigen retrieval?

Start with heat-mediated EDTA retrieval at pH 8.0 for the PB9733 paraffin-section assay (datasheet PB9733). The selected tissue image used this retrieval before incubation with 1 μg/ml primary antibody overnight at 4°C (PB9733 tissue-IHC caption). If staining is weak, check that sections experienced consistent heating and cooling, then adjust retrieval duration while retaining the documented buffer (standard IHC practice). Compare changes on matched sections with a positive tissue control, since uneven retrieval can resemble patchy antigen expression (standard IHC practice). Record retrieval conditions alongside staining intensity so the comparison remains interpretable (standard IHC practice).

Can fixation explain weak or uneven PAK5 staining in paraffin sections?

Target-specific fixation sensitivity for PAK5 is unknown: the selected paraffin-section caption does not state its fixative (PB9733 tissue-IHC caption). Compare sections with documented fixation and processing histories before attributing different staining intensities to PAK5 abundance (standard IHC practice). Keep section handling, heat-mediated EDTA retrieval at pH 8.0, and primary incubation conditions consistent across that comparison (datasheet PB9733; standard IHC practice). Examine tissue preservation and staining at section edges, where processing differences can complicate interpretation (standard IHC practice). Neither the reported tissue pattern nor PAK5 topology establishes a PAK5-specific fixation effect (HPA tissue IHC; UniProt Q9P286 topology).

Which staining compartments are plausible for PAK5 in tissue IHC?

Assess PAK5 signal primarily in the cytoplasmic compartment when comparing tissue sections with the reported CNS staining pattern (HPA tissue IHC). Mitochondrial, cytoplasmic and nuclear locations are described for PAK5, including shuttling between nucleus and mitochondria (UniProt Q9P286 subcellular). Supported cell-imaging locations include nucleoplasm, nuclear membrane, cytosol and mitochondria, although those observations do not establish how each will appear with chromogenic tissue IHC (HPA subcellular). Review the counterstain and cellular boundaries before assigning a brown deposit to a nucleus or cytoplasm (standard IHC practice). Record compartment scores separately when a specimen shows more than one pattern (standard IHC practice).

How should epitope uncertainty affect interpretation of PAK5 staining?

The supplied record lists 0 isoforms and a 1–719 amino-acid chain, but gives no antibody epitope location (UniProt Q9P286; PB9733 tissue-IHC caption). PAK5 contains a CRIB region at residues 11–24 and a kinase domain at 449–700; these boundaries alone cannot identify what PB9733 recognizes (UniProt Q9P286 domains). Phosphoserine 104 and phosphothreonine 107 are reported, without evidence here that either modification changes this antibody’s tissue staining (UniProt Q9P286 modified residues). Keep retrieval and detection conditions matched when comparing specimens, and avoid interpreting a staining difference as an isoform or phosphorylation difference without epitope-specific validation (standard IHC practice).

How can IF help investigate an ambiguous PAK5 IHC pattern?

Use IF as a separate follow-up to localize cells underlying an ambiguous chromogenic pattern, rather than treating the paraffin-section IHC conditions as an IF protocol (standard IHC/IF practice; PB9733 tissue-IHC caption). Multiplex PAK5 with a marker for the expected cell type; neuronal cells in cerebral cortex and hippocampus provide relevant reported contexts (HPA tissue IHC). Choose spectrally separated fluorophores and a channel with low tissue autofluorescence, and inspect single-channel controls before judging overlap (standard IF practice). Because PAK5 is intracellular and has no transmembrane segment, select permeabilisation appropriate to the compartment and antibody epitope being assessed; its epitope is unspecified here (UniProt Q9P286 topology; standard IF practice).

What causes diffuse brown signal in a PAK5 IHC section?

First inspect a no-primary control to distinguish detection-system deposits from antibody-dependent staining (standard IHC practice). The selected assay used 10% goat serum, a biotinylated goat anti-rabbit secondary, a streptavidin-biotin complex and DAB, so evaluate blocking and detection reagents when diffuse brown signal appears (PB9733 tissue-IHC caption). Include a peroxidase-block step and check for endogenous biotin-related signal when using this detection format (standard IHC practice). Titrate exposure to the documented 1 μg/ml primary condition and compare matched sections before calling diffuse signal positive (PB9733 tissue-IHC caption; standard IHC practice). HPA reports presumed off-target binding, which warrants particular caution with unexpected staining (HPA tissue IHC).

How should I quantify PAK5 across differently stained tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION

Define the cell population and compartment before scoring, using the reported cytoplasmic CNS pattern as one tissue-IHC reference (HPA tissue IHC). Score the percentage of positive cells and staining intensity, or calculate an H-score from intensity categories, using the same thresholds across sections (standard IHC practice). For a spatial analysis, report positive-cell density per mm² of viable tissue and normalize counts to the annotated area (standard IHC practice). Keep retrieval at pH 8.0 and detection conditions consistent across compared specimens (datasheet PB9733; standard IHC practice). Document excluded necrotic or damaged regions and retain separate cytoplasmic and nuclear scores if both patterns occur (standard IHC practice).

When is a PAK5-positive result convincing rather than artefactual?

A convincing result has cellular staining in a plausible compartment and survives comparison with negative and no-primary controls (UniProt Q9P286 subcellular; standard IHC practice). Reported neuronal staining in cerebral cortex and hippocampus, and cytoplasmic CNS expression, provide context for expected cells; they do not validate every positive deposit (HPA tissue IHC). Treat staining confined to section edges, necrotic regions or damaged cells cautiously, and investigate brown deposits reproduced without primary antibody as possible endogenous enzyme or detection signal (standard IHC practice). HPA marks its tissue staining approved while explicitly noting presumed off-target binding, so unexpected cells or compartments require independent corroboration (HPA tissue IHC).

Boster reagents

Best PAK5 / Serine/threonine-protein kinase PAK 5 IHC Antibodies

PB9733 has real chromogenic IHC data from human paraffin sections of glioma and cerebellum (PB9733 image captions). No IF image is supplied (catalog).

Real IHC data

Anti-PAK5/PAK7 Antibody ®

Cat # PB9733

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PB9733 was shown staining human glioma and cerebellum paraffin sections with DAB detection (PB9733 image captions). Its listed applications are IHC and WB, and its listed reactivity is Human, Mouse and Rat (catalog).

Which to pick: Choose PB9733 for paraffin-section IHC: its captions show heat retrieval in EDTA at pH 8.0 and DAB detection (PB9733 image captions); the fixative is unreported (PB9733 image captions). No listed SKU is validated for IF/ICC (catalog applications and images). PB9733 lists Mouse and Rat reactivity, but its supplied IHC images show human tissue only (catalog reactivity; PB9733 image captions).

Each figure is that product's own IHC / IF validation image from its datasheet.

References

UniProt Consortium. UniProt entry Q9P286 (PAK5_HUMAN, Serine/threonine-protein kinase PAK 5).
Human Protein Atlas. PAK5 tissue IHC expression (reliability: Approved).
Human Protein Atlas. PAK5 subcellular location (ICC-IF): Mainly localized to the nucleoplasm. In addition localized to the nuclear membrane, cytosol and mitochondria..
Human Protein Atlas. PAK5 antibody validation summary (2 antibodies).
Correlation between chemotherapy resistance in osteosarcoma patients and PAK5 and Ezrin gene expression. Oncology letters 2018 — PMC5769406.
PAK5-mediated phosphorylation and nuclear translocation of NF-κB-p65 promotes breast cancer cell proliferation in vitro and in vivo. Journal of experimental & clinical cancer research : CR 2017 — PMC5645986.
Efficient inhibition of human glioma development by RNA interference-mediated silencing of PAK5. International journal of biological sciences 2015 — PMC4308408.
PAK5 drives vascular remodeling in hypoxic pulmonary hypertension via Drp1-dependent mitochondrial midzone division. Scientific reports 2026 — PMC13187325.
PubMed PMID:12032833 — UniProt-cited evidence.
PubMed PMID:10574462 — UniProt-cited evidence.
PubMed PMID:14702039 — UniProt-cited evidence.