Seroatlas · Human Serome Atlas

KCTD21

BTB/POZ domain-containing protein KCTD21

Also known as: KCASH2, KCD21_HUMAN

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession: Q4G0X4
Gene: KCTD21
Ensembl: ENSG00000188997
Chromosome: 11
Canonical length: 260 aa
Protein class: Predicted intracellular proteins
Subcellular location: Cytosol
Quaternary structure: Homopentamer

OverviewNCBI Gene

Enables cullin family protein binding activity; histone deacetylase binding activity; and identical protein binding activity. Involved in negative regulation of smoothened signaling pathway and ubiquitin-dependent protein catabolic process. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

260 residues, UniProt reviewed canonical sequence.

>Q4G0X4|KCTD21
     1  MSDPITLNVG GKLYTTSLAT LTSFPDSMLG AMFSGKMPTK RDSQGNCFID RDGKVFRYIL
    61  NFLRTSHLDL PEDFQEMGLL RREADFYQVQ PLIEALQEKE VELSKAEKNA MLNITLNQRV
   121  QTVHFTVREA PQIYSLSSSS MEVFNANIFS TSCLFLKLLG SKLFYCSNGN LSSITSHLQD
   181  PNHLTLDWVA NVEGLPEEEY TKQNLKRLWV VPANKQINSF QVFVEEVLKI ALSDGFCIDS
   241  SHPHALDFMN NKIIRLIRYR

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against KCTD21 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability: Unknown
Secreted: No
Transmembrane segments: 0
Mean surface accessibility (rSASA): 0.3
Highest tissue expression: 15 nTPM

Expression across tissuesHPA

Tissue

liver: 15 nTPM
adrenal gland: 13 nTPM
midbrain: 11 nTPM
thyroid gland: 10 nTPM
ovary: 10 nTPM
blood vessel: 10 nTPM

Single-cell type

adrenal medulla cells: 32 nCPM
esophageal apical cells: 29 nCPM
adrenal cortex cells: 26 nCPM
neutrophils: 21 nCPM
gonadotrophs: 19 nCPM
esophageal suprabasal cells: 16 nCPM

Immune cell

neutrophil: 8.3 nTPM
eosinophil: 7.5 nTPM
intermediate monocyte: 6 nTPM
classical monocyte: 5.4 nTPM
non-classical monocyte: 5.1 nTPM
myeloid DC: 3.7 nTPM

Brain region

midbrain: 40 nTPM
pons: 37 nTPM
medulla oblongata: 36 nTPM
hypothalamus: 35 nTPM
white matter: 35 nTPM
thalamus: 35 nTPM

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance): 1.68
gnomAD pLI: 0
gnomAD missense Z: 0.5
DepMap mean gene effect: -0.04
DepMap dependency class: selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 6% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of KCTD21 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

KCTD11

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads KCTD21 as an antibody target. Whether an autoantibody or antibody against KCTD21 could matter depends on whether native KCTD21 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

KCTD21 is annotated as predominantly intracellular. Intracellular proteins are common autoantibody markers, becoming visible to the immune system after cell injury or altered processing, but are usually markers of disease rather than direct drivers.

Annotation status

The present source text does not explicitly label KCTD21 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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