PSAP / Prosaposin · IHC design guide

Design Immunohistochemistry for PSAP

Plan PSAP staining in paraffin sections with the IHC-validated antibody at 2–5 μg/ml (datasheet A00937-1). Use the granular cytoplasmic tissue pattern to assess staining and consider PSAP secretion when interpreting signal (HPA tissue IHC; UniProt).

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

Immunohistochemistry protocol sheet for PSAP (IHC for PSAP): expected localisation Granular cytoplasm in tissue sections (HPA tissue IHC), antibody A00937-1, validated IHC image, and IHC protocol steps — Printable **PSAP** IHC protocol sheet — expected localisation Granular cytoplasm in tissue sections (HPA tissue IHC), antibody A00937-1, controls and protocol steps. Open the full PSAP IHC guide →

Navigate to: Protocols Staining pattern Controls Antibodies

PSAP 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	Granular cytoplasm in tissue sections (HPA tissue IHC)
	Staining pattern	Granular cytoplasm in adipocytes and glandular cells (HPA tissue IHC)
	Antigen retrieval	EDTA pH 8.0 HIER, heat-mediated (datasheet A00937-1)
	Positive control ⓘ	Adipose tissue+4 more · see all
	Negative control ⓘ	None in HPA (detected in all 45 tissues); use no-primary + isotype controls

Important caveats

Reasons your staining may differ from the expected pattern.

	Fixation	Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A00937-1)
	Caveat	Secreted PSAP may contribute extracellular signal (UniProt)
	Regulation	Low tissue specificity; no regulator specified (HPA tissue IHC; UniProt)
	Isoform / epitope	3 isoforms; cleavage into saposins affects epitope coverage (UniProt)

Section 1

Recommended PSAP IHC & IF Protocols

The catalog antibody has a datasheet IHC-P protocol (datasheet: A00937-1). The published IHC methods below provide sample-specific retrieval, staining and detection conditions (cited PMC articles).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Paraffin-embedded human thyroid papillary carcinoma tissue; fixative not specified (datasheet A00937-1)
Fixation	Image fixative and duration unreported (datasheet A00937-1); 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 A00937-1); 20 min, 95–100 °C (standard)
Peroxidase block	3% H2O2, 10 min, room temperature (standard)
Blocking	10% goat serum (datasheet A00937-1)
Primary antibody	Rabbit anti-PSAP, 2-5 μg/ml (datasheet A00937-1)
Primary incubation	Overnight at 4 °C (datasheet A00937-1)
Detection	HRP-conjugated secondary, DAB chromogen (datasheet A00937-1)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	PSAP-positive staining in adipocytes of adipose tissue (HPA tissue IHC: High). HPA tissue profile: Granular cytoplasmic expression in all tissues. No signal in the no-primary control.

💡Decision noteStart with heat-mediated EDTA retrieval at pH 8.0 for the catalog antibody (datasheet: A00937-1). Treat published retrieval conditions as antibody-specific starting points (cited PMC articles).

Section 2

What Is the Expected PSAP Staining Pattern?

PSAP should show granular cytoplasmic staining in cells across tissues (HPA: Supported; granular cytoplasmic expression in all tissues). High staining is reported in adipocytes, glandular cells, hematopoietic cells, respiratory epithelial cells and glia (HPA: tissue IHC). Its lysosomal location supports an intracellular punctate pattern; PSAP is also secreted and has no transmembrane segment (UniProt P07602: location and topology).

What am I looking at on my slide?
Granular cytoplasmic staining in expected cells, including adipocytes or glandular cells.	This matches the reported tissue pattern (HPA: granular cytoplasmic expression in all tissues; High in adipocytes and glandular cells). Score cellular intensity and distribution separately (general IHC practice).
Strong, predominantly nuclear staining with little cytoplasmic granularity.	That compartment conflicts with the supported vesicular pattern (HPA: ICC-IF vesicles) and lysosomal location (UniProt P07602). Consider detection artefact before calling it PSAP.
Staining confined to a cell type that does not match the expected pattern in the examined tissue.	Check the tissue-specific reference first (HPA: tissue IHC). Cross-reactivity or endogenous detection activity is possible, but staining alone cannot distinguish them (general IHC practice).
Diffuse colour across cells and surrounding tissue obscures granules.	The result cannot be scored reliably against the granular cytoplasmic reference (HPA: tissue IHC). Background from antibody binding or detection chemistry is possible (general IHC practice).
No detectable signal in an otherwise interpretable adrenal gland or appendix section.	Both have High glandular-cell staining in HPA tissue IHC. Check assay performance before inferring biological absence; HPA staining does not establish a fixation effect.

💡Expected PSAP appearanceCall positive when expected cells show clear granular cytoplasmic staining, with High intensity possible in HPA-listed cells (HPA: tissue IHC); dominant nuclear colour is discordant (HPA: vesicles; UniProt P07602: lysosome).

How each factor affects the staining
Compartment and secretion	PSAP is lysosomal and secreted, with no transmembrane segment (UniProt P07602). Interpret extracellular colour cautiously alongside cellular granules; secretion alone cannot validate a deposit.
Precursor processing	Prosaposin is cleaved into saposins A–D (UniProt P07602: processing). The recognized form depends on an antibody's epitope; no epitope is supplied here.
Glycosylation	Five glycosylation sites are annotated (UniProt P07602: residues 80, 101, 215, 332, 426). This record gives no target-specific prediction for antigen retrieval or fixation sensitivity.
Isoforms and antibody validation	Three isoforms are annotated (UniProt P07602). HPA004426 and CAB004647 have Supported IHC status (HPA: antibodies); that status does not establish identical isoform recognition.
IF/ICC Q&A: What should fluorescence show?	Expect vesicular signal (HPA: ICC-IF, supported), consistent with lysosomal PSAP (UniProt P07602). ICC-IF images exist for A-431, U-251MG and U2OS (HPA: subcellular).

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
Known-positive tissue lacks granular signal.	Assay failure is possible when expected High cells are blank (HPA: adrenal and appendix glandular cells).	Review the catalog antibody's IHC-P instructions, retrieval conditions and detection controls (general IHC practice); target-specific fixation sensitivity is unreported.
Nuclei dominate the stain.	The pattern conflicts with vesicular localisation (HPA: ICC-IF) and lysosomal localisation (UniProt P07602).	Check a no-primary control and inspect counterstain or detection artefacts before assigning PSAP positivity (general IHC practice).
Unexpected cell types stain strongly.	Cross-reactivity or endogenous detection activity may contribute (general IHC practice); PSAP is broadly expressed (HPA: tissue IHC).	Compare the exact cell type with HPA tissue images, then assess no-primary and detection controls (HPA: tissue IHC; general IHC practice).
Diffuse background hides cellular granules.	Nonspecific binding or detection background can obscure the expected pattern (general IHC practice; HPA: granular cytoplasmic expression).	Review blocking, antibody dilution, washes and chromogen development using appropriate controls (general IHC practice).
Extracellular colour appears without clear cell-associated granules.	PSAP can be secreted (UniProt P07602), but extracellular colour alone does not establish specific staining.	Compare nearby cellular staining and a no-primary control; report the extracellular finding separately (general IHC practice).
IF/ICC appears diffuse instead of vesicular.	Diffuse fluorescence differs from the supported vesicular reference (HPA: ICC-IF subcellular summary).	Check background controls, focus and permeabilisation conditions before interpreting the signal (general IF practice); use the separate IF/ICC guide for workflow.

Source: UniProt P07602 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing PSAP staining

IHC analysis of PSAP using anti-PSAP antibody (A00937-1). PSAP was detected in a paraffin-embedded section of human thyroid papillary carcinoma 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-PSAP Antibody (A00937-1) 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.

A00937-1 · IHCIHC analysis of PSAP using anti-PSAP antibody (A00937-1). PSAP was detected in a paraffin-embedded section of human thyroid papillary carcin

IHC analysis of PSAP using anti-PSAP antibody (A00937-1). PSAP was detected in a paraffin-embedded section of human tonsil 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-PSAP Antibody (A00937-1) 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.

A00937-1 · IHCIHC analysis of PSAP using anti-PSAP antibody (A00937-1). PSAP was detected in a paraffin-embedded section of human tonsil tissue. Heat medi

IF analysis of PSAP using anti-PSAP antibody (A00937-1). PSAP was detected in an immunocytochemical section of A549 cells. Enzyme antigen retrieval was performed using IHC enzyme antigen retrieval reagent (AR0022) for 15 mins. The cells were blocked with 10% goat serum. And then incubated with 5 μg/mL rabbit anti-PSAP Antibody (A00937-1) overnight at 4°C. DyLight®488 Conjugated Goat Anti-Rabbit IgG (BA1127) was used as secondary antibody at 1:100 dilution and incubated for 30 minutes at 37°C. The section was counterstained with DAPI. Visualize using a fluorescence microscope and filter sets appropriate for the label used.

A00937-1 · IFIF analysis of PSAP using anti-PSAP antibody (A00937-1). PSAP was detected in an immunocytochemical section of A549 cells. Enzyme antigen re

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000197746-PSAP/tissue/cerebral+cortex#imid_1608536

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000197746-PSAP/tissue/colon#imid_1608454

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000197746-PSAP/tissue/liver#imid_1608471

HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000197746-PSAP/tissue/kidney#imid_1608472

HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA004426; green = PSAP, blue = nucleus, red = microtubules.

← swipe / scroll for more images →

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

Sample controls for PSAP IHC & IF

🧪Run adipose tissue first; adipocytes should stain (HPA: High in adipocytes). HPA detects PSAP in all 45 scored tissues, so there is no supported negative tissue; use no-primary and isotype controls, and treat unstained stromal cells on the positive slide as candidate internal negatives only after confirming their identity and background (HPA: no negative tissue rows).

Positive control tissue: Adipose tissue (Adipocytes, HPA High)

Negative control tissue: None in HPA: PSAP is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead.

ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show PSAP in A-431, U-251MG, U2OS, with annotated localisation: Vesicles (supported) (HPA subcellular).

Technical controls: Include a no-primary, secondary-only slide, a rabbit IgG isotype control matched to the primary antibody’s clonality (catalog caption: rabbit anti-PSAP), and PSAP-knockout material or immunizing-peptide competition as a biological specificity control. For adipose tissue, check lipid-related spaces and nonspecific chromogen deposition against the control slides (HPA: High in adipocytes).

⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected A00937-1 paraffin-section caption does not state its fixative (catalog caption: fixative not stated). The caption documents heat retrieval in EDTA at pH 8.0 for paraffin IHC, but does not establish whether retrieval is required under other conditions (catalog caption: EDTA pH 8.0). Frozen sections and IF cannot be ranked as easier from the supplied evidence; adipocyte lipid spaces require careful interpretation in the proposed positive tissue (HPA: High in adipocytes).

HPA tissue IHC evidence for PSAP

Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — 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
Adipose tissue	Adipocytes	High	Protein (IHC)	HPA →
Adrenal gland	Glandular cells	High	Protein (IHC)	HPA →
Appendix	Glandular cells	High	Protein (IHC)	HPA →
Bone marrow	Hematopoietic cells	High	Protein (IHC)	HPA →
Breast	Glandular cells	High	Protein (IHC)	HPA →

Undetected expression · recommended negative controls

Tissue	Cell type	Level	Evidence	Source
None in HPA: PSAP is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead.

Section 3

Advanced PSAP IHC Tips

Troubleshoot PSAP staining by checking retrieval, tissue processing, cellular pattern, antibody epitope and detection controls (datasheet A00937-1; HPA tissue IHC; UniProt P07602).

How should I retrieve PSAP in paraffin sections when staining is weak?

Start with heat-mediated retrieval in EDTA at pH 8.0 (datasheet A00937-1). The catalog antibody produced PSAP staining in a paraffin section of human thyroid papillary carcinoma using that retrieval condition and 2 μg/ml primary antibody overnight at 4°C (datasheet A00937-1). If staining remains weak, compare retrieval heating and cooling conditions on adjacent sections while holding antibody concentration and DAB development constant (standard IHC practice). Judge improvement by a granular cytoplasmic pattern and an appropriate negative control, rather than by stronger brown signal alone (HPA tissue IHC; standard IHC practice).

Could fixation explain inconsistent PSAP staining between paraffin blocks?

Target-specific fixation sensitivity is unknown because the selected paraffin-section caption does not state a fixative or fixation duration (datasheet A00937-1). Record each block’s fixative, fixation time and processing history before comparing staining across cases (standard IHC practice). Run sections from the blocks together using EDTA retrieval at pH 8.0 and the same antibody concentration, detection and DAB development conditions (datasheet A00937-1; standard IHC practice). If differences persist, assess tissue preservation and control staining before attributing them to PSAP biology; neither the tissue staining profile nor protein topology establishes a fixation effect (HPA tissue IHC; UniProt P07602; standard IHC practice).

Where should PSAP staining appear, and how should extracellular signal be assessed?

Expect mainly granular cytoplasmic staining in tissue sections, consistent with lysosomal PSAP and vesicular localisation (HPA tissue IHC; HPA subcellular; UniProt P07602). PSAP is also secreted, so extracellular signal can be biologically plausible, but its location alone cannot establish specificity (UniProt P07602; standard IHC practice). Compare the suspected signal with cell outlines, tissue structure and negative controls at the same DAB development setting (standard IHC practice). Treat a predominantly nuclear or uniformly diffuse pattern as a reason to recheck retrieval, background and antibody controls before scoring it as PSAP (HPA tissue IHC; standard IHC practice).

Can this stain distinguish intact prosaposin from individual saposins?

Do not assign a brown deposit to intact prosaposin without an epitope map: the precursor is processed into saposins A, B, C and D (UniProt P07602; standard IHC interpretation). Those chains occupy distinct regions, including saposin A at residues 60–142 and saposin D at 405–486 (UniProt P07602). PSAP also has 3 annotated isoforms and glycosylation sites at residues 80, 101, 215, 332 and 426, so epitope identity matters when comparing staining across reagents (UniProt P07602; standard IHC interpretation). Obtain the catalog antibody’s immunogen or epitope information before claiming isoform or cleavage-product specificity; morphology alone cannot resolve those forms (standard IHC interpretation).

How can IF help assess the cellular source of PSAP IHC staining?

Use IF as a separate confirmation experiment and multiplex PSAP with an adipocyte marker in adipose tissue, where adipocytes show high PSAP staining (HPA: High in adipocytes; standard IF practice). Choose spectrally separated fluorophores, favouring a far-red channel for the weaker signal when tissue autofluorescence compromises shorter wavelengths (standard IF practice). Determine whether the antibody epitope is intracellular before selecting permeabilisation: lysosomal PSAP requires access to an intracellular compartment, while PSAP can also be secreted (UniProt P07602; standard IF practice). Compare cellular overlap and punctate signal with single-label and secondary-only controls; IF conditions should be established independently of the paraffin IHC caption (HPA subcellular; standard IF practice).

What should I check when PSAP DAB staining looks widespread?

First compare the section with a no-primary control and inspect whether brown signal follows tissue edges, damaged areas or the expected granular cytoplasm (HPA tissue IHC; standard IHC practice). Block endogenous peroxidase and assess secondary-antibody background before changing the primary antibody concentration (standard chromogenic IHC practice). The selected image used 2 μg/ml primary antibody overnight at 4°C, an anti-rabbit peroxidase secondary and DAB detection (datasheet A00937-1). Because PSAP can be secreted, extracellular staining deserves control-based evaluation; a diffuse brown haze without cellular structure is insufficient evidence of specific PSAP staining (UniProt P07602; standard IHC interpretation).

How should I quantify PSAP staining across tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION

Define the cell population and tissue region before scoring, then record the percentage of positive cells and cytoplasmic intensity on a 0–3 scale (standard IHC scoring practice). An H-score from 0–300 combines those intensity categories with their cell percentages; report the scoring rules and threshold used (standard IHC scoring practice). For patchy tissue, also report positive-cell density per mm² of viable tissue or per defined cell population, excluding necrosis and section edges (standard IHC scoring practice). Keep retrieval, imaging and DAB development consistent, and normalise comparisons to the same viable compartment because PSAP staining is granular and broadly distributed across tissues (HPA tissue IHC; standard IHC practice).

Which PSAP patterns support a true positive rather than an artefact?

A credible positive shows granular cytoplasmic staining in identifiable cells, matching the supported tissue profile and vesicular localisation (HPA tissue IHC; HPA subcellular). High staining has been reported in adipocytes and several glandular and hematopoietic cell populations, so identify the stained cell type before comparing cases (HPA tissue IHC). Predominantly nuclear staining, edge enhancement, necrotic deposits or signal reproduced in a no-primary control should prompt review of background and endogenous peroxidase activity (HPA tissue IHC; standard IHC practice). Extracellular signal is possible because PSAP is secreted, but interpret it alongside morphology and controls rather than treating it as proof of specific staining (UniProt P07602; standard IHC interpretation).

Boster reagents

Best PSAP / Prosaposin IHC Antibodies

Anti-PSAP A00937-1 has human paraffin-section IHC, A549 ICC/IF, and human thyroid-cancer IF examples (catalog image captions); M00937 is listed for human IHC (catalog applications/reactivity).

Real IHC data

Anti-PSAP Antibody ®

Cat # A00937-1

View product →

A00937-1 has IHC images from human thyroid papillary carcinoma and tonsil paraffin sections, plus IF images from A549 cells and a human thyroid-cancer paraffin section (catalog image captions). M00937 is listed for human IHC, but has no IHC image or documented sample type in the payload (catalog applications/reactivity; IHC image captions).

Which to pick: For tissue IHC, choose A00937-1 when image-backed human paraffin-section evidence matters; its IHC captions report EDTA retrieval and 2 μg/ml primary antibody, but do not report the fixative (A00937-1 IHC image captions). For IF/ICC, choose A00937-1 because its application list and images cover both; M00937 is a rabbit monoclonal, clone 24P28, listed for IHC without an IF/ICC application or image (catalog applications; catalog clone; image captions). Neither SKU has documented cross-species reactivity in this payload (catalog reactivity: Human for both).

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

References

UniProt Consortium. UniProt entry P07602 (SAP_HUMAN, Prosaposin).
Human Protein Atlas. PSAP tissue IHC expression (reliability: Supported).
Human Protein Atlas. PSAP subcellular location (ICC-IF): Localized to vesicles..
Human Protein Atlas. PSAP antibody validation summary (2 antibodies).
Diagnostic Role and Prognostic Impact of PSAP Immunohistochemistry: A Tissue Microarray Study on 31,358 Cancer Tissues. Diagnostics (Basel, Switzerland) 2023 — PMC10606209.
Prostate-specific antigen and hormone receptor expression in male and female breast carcinoma. Diagnostic pathology 2010 — PMC2954973.
The expression of prosaposin and its receptors, GRP37 and GPR37L1, are increased in the developing dorsal root ganglion. PloS one 2021 — PMC8357083.
Increased expression of the proapoptotic presenilin associated protein is involved in neuronal tangle formation in human brain. Scientific reports 2024 — PMC11512019.
PubMed PMID:2515150 — UniProt-cited evidence.
PubMed PMID:2498298 — UniProt-cited evidence.
PubMed PMID:15164054 — UniProt-cited evidence.