TSSK4

Summary

TSSK4 (testis specific serine kinase 4, HGNC:19825) is a protein-coding gene on chromosome 14q12, encoding Testis-specific serine/threonine-protein kinase 4 (Q6SA08). Serine/threonine kinase which is involved in male germ cell development and in mature sperm function.

This gene encodes a member of the testis-specific serine/threonine kinase family. The encoded protein is thought to be involved in spermatogenesis via stimulation of the CREB/CRE responsive pathway through phosphorylation of the cAMP responsive element binding protein transcription factor. Alternative splicing results in multiple transcript variants.

Source: NCBI Gene 283629 — RefSeq curated summary.

At a glance

• Clinical variants (ClinVar): 40 total
• Druggable target: yes
• MANE Select transcript: NM_001184739

Identifiers

Gene identifiers

Field	Value
HGNC ID	HGNC:19825
Approved symbol	TSSK4
Name	testis specific serine kinase 4
Location	14q12
Locus type	gene with protein product
Status	Approved
Ensembl gene	ENSG00000139908
Ensembl biotype	protein_coding
OMIM	610711
Entrez	283629

Gene structure

Transcript identifiers

Ensembl transcripts: 7 — 6 protein_coding, 1 retained_intron

ENST00000287913, ENST00000339917, ENST00000428351, ENST00000553766, ENST00000554420, ENST00000555092, ENST00000556621

RefSeq mRNA: 3 — MANE Select: NM_001184739 NM_001184739, NM_001308067, NM_174944

CCDS: CCDS53890, CCDS76662, CCDS9618

Canonical transcript exons

ENST00000339917 — 4 exons

Exon	Start	End
ENSE00001389937	24207116	24207509
ENSE00002253090	24205696	24206148
ENSE00003537995	24207964	24208248
ENSE00003589369	24206509	24206723

Expression profiles

Bgee: expression breadth ubiquitous, 134 present calls, max score 91.47.

FANTOM5 (CAGE): breadth tissue_specific, TPM avg 0.0512 / max 48.7172, expressed in 4 samples.

FANTOM5 promoters (3 alternative TSS)

Promoter ID	TPM avg	Samples expressed
139008	0.0399	4
139009	0.0061	3
139010	0.0052	3

Top tissues by expression

134 total, by Bgee expression score (0-100, higher = more expressed):

Tissue	Anatomy ID	Expression score	Quality
left testis	UBERON:0004533	91.47	gold quality
male germ line stem cell (sensu Vertebrata) in testis	CL:0000089 ∩ UBERON:0000473	91.34	gold quality
testis	UBERON:0000473	91.00	gold quality
right testis	UBERON:0004534	90.74	gold quality
monocyte	CL:0000576	82.20	gold quality
leukocyte	CL:0000738	81.56	gold quality
sural nerve	UBERON:0015488	79.43	gold quality
endometrium	UBERON:0001295	78.34	gold quality
rectum	UBERON:0001052	77.93	gold quality
bone marrow	UBERON:0002371	76.90	gold quality
mucosa of stomach	UBERON:0001199	76.24	gold quality
cerebellum	UBERON:0002037	76.13	gold quality
cerebellar cortex	UBERON:0002129	76.06	gold quality
cerebellar hemisphere	UBERON:0002245	76.04	gold quality
granulocyte	CL:0000094	75.96	gold quality
smooth muscle tissue	UBERON:0001135	75.86	gold quality
blood	UBERON:0000178	75.74	gold quality
lymph node	UBERON:0000029	75.68	gold quality
vermiform appendix	UBERON:0001154	75.49	gold quality
right hemisphere of cerebellum	UBERON:0014890	75.48	gold quality
bone marrow cell	CL:0002092	75.42	gold quality
right coronary artery	UBERON:0001625	75.28	gold quality
small intestine	UBERON:0002108	75.19	gold quality
small intestine Peyer’s patch	UBERON:0003454	75.07	gold quality
tonsil	UBERON:0002372	74.96	gold quality
uterine cervix	UBERON:0000002	74.81	gold quality
descending thoracic aorta	UBERON:0002345	74.76	gold quality
corpus callosum	UBERON:0002336	74.68	gold quality
transverse colon	UBERON:0001157	74.52	gold quality
stromal cell of endometrium	CL:0002255	74.50	gold quality

Single-cell (SCXA)

Detected in 1 experiment(s), a significant marker in 0.

Experiment	Marker?	Max mean expression
E-ANND-3	no	0.57

Regulation

Is transcription factor: no

miRNA regulators (miRDB)

2 targeting TSSK4, top 30 by miRDB confidence (max_score; target_count = how many genes the miRNA targets in total — lower means more specific):

miRNA	Max score	Avg score	miRNA target_count
HSA-MIR-499B-5P	98.35	68.39	988
HSA-MIR-4494	97.86	64.93	850

Literature-anchored findings (GeneRIF, showing 2)

• association of some single nucleotide polymorphisms in TSSK4 with male infertility. (PMID:18390560)
• TSSK4 was able to induce cell apoptosis in vitro depending on its kinase activity, which leads to abnormal testes weight and apoptosis, shedding light on its function in the process of spermatogenesis and/or spermiogenesis (PMID:25877358)

Cross-species orthologs

5 orthologs

Organism	Symbol	Gene ID
danio_rerio	nim1kb	ENSDARG00000079031
mus_musculus	Tssk4	ENSMUSG00000007591
rattus_norvegicus	Tssk4	ENSRNOG00000019789
drosophila_melanogaster	CG9222	FBGN0031784
caenorhabditis_elegans	F23C8.8	WBGENE00017737

Paralogs (17): NUAK1 (ENSG00000074590), PRKAA1 (ENSG00000132356), HUNK (ENSG00000142149), SIK1 (ENSG00000142178), BRSK1 (ENSG00000160469), SIK3 (ENSG00000160584), PRKAA2 (ENSG00000162409), TSSK3 (ENSG00000162526), NUAK2 (ENSG00000163545), SNRK (ENSG00000163788), MELK (ENSG00000165304), SIK2 (ENSG00000170145), BRSK2 (ENSG00000174672), NIM1K (ENSG00000177453), TSSK6 (ENSG00000178093), TSSK2 (ENSG00000206203), TSSK1B (ENSG00000212122)

Protein

Protein identifiers

Testis-specific serine/threonine-protein kinase 4 — Q6SA08 (reviewed: Q6SA08)

Alternative names: Serine/threonine-protein kinase 22E

All UniProt accessions (4): Q6SA08, H0YJ36, H0YJB1, H7C3J1

UniProt curated annotations — full annotation on UniProt →

Function. Serine/threonine kinase which is involved in male germ cell development and in mature sperm function. May be involved in the Cre/Creb signaling pathway. Phosphorylates CREB1 on ‘Ser-133’ in vitro and can stimulate Cre/Creb pathway in cells. Phosphorylates CREM on ‘Ser-116’ in vitro. Phosphorylates ODF2 on ‘Ser-95’.

Subunit / interactions. Homodimer. Interacts with HSP90; this interaction stabilizes and activates TSSK4. Interacts with ODF2 (via C-terminus); this interaction promotes ODF2 phosphorylation on ‘Ser-95’. May interact with CREM. Interacts with CREB1; this interaction facilitates phosphorylation on ‘Ser-133’. Interacts with QRICH2.

Subcellular location. Cytoplasmic vesicle. Secretory vesicle. Acrosome. Cell projection. Cilium. Flagellum.

Tissue specificity. Expressed only in the testis.

Post-translational modifications. Activated by autophosphorylation on Thr-197. ODF2 potentiates the autophosphorylation activity of TSSK4 at Thr-197. Ubiquitinated; HSP90 activity negatively regulates ubiquitination and degradation.

Activity regulation. Activated by phosphorylation on Thr-197.

Similarity. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family.

Isoforms (3)

UniProt ID	Names	Canonical?
Q6SA08-1	1	yes
Q6SA08-2	2
Q6SA08-3	3

RefSeq proteins (3): NP_001171668, NP_001294996, NP_777604 (=MANE)

Domains & families (InterPro)

ID	Name	Type
IPR000719	Prot_kinase_dom	Domain
IPR008271	Ser/Thr_kinase_AS	Active_site
IPR011009	Kinase-like_dom_sf	Homologous_superfamily
IPR017441	Protein_kinase_ATP_BS	Binding_site
IPR047908	TSSK4_cat	Domain

Pfam: PF00069

Enzyme classification (BRENDA):

• EC 2.7.11.1 — non-specific serine/threonine protein kinase (BRENDA: 71 organisms, 682 substrates, 228 inhibitors, 23 Km, 6 kcat entries)

Substrate kinetics (BRENDA)

8 substrates with measured Km, best-characterized 8. Km ranges are aggregated across organisms/conditions.

Substrate	Km (mM)	Measurements
ATP	0.0007–0.64	11
KKRAARATSNVFA	0.013–0.045	3
PAH1 PHOSPHATIDATE PHOSPHATASE	0.0002	2
RRRLSSLRA	0.0036–0.0037	2
GTP	0.46	1
KKRAARASSNVFA	0.02	1
LYS-LYS-PHE-ASN-ARG-THR-LEU-SER-VAL-ALA	0.0093	1
MYELIN BASIC PROTEIN	0.145	1

Catalyzed reactions (Rhea), 2 shown:

• L-seryl-[protein] + ATP = O-phospho-L-seryl-[protein] + ADP + H(+) (RHEA:17989)
• L-threonyl-[protein] + ATP = O-phospho-L-threonyl-[protein] + ADP + H(+) (RHEA:46608)

UniProt features (15 total): sequence variant 5, binding site 2, splice variant 2, chain 1, domain 1, mutagenesis site 1, sequence conflict 1, active site 1, modified residue 1

Structure

Experimental structures (PDB)

0 structures.

Predicted structure (AlphaFold)

Model	pLDDT	Fraction very-high
AF-Q6SA08-F1	86.86	0.70

Functional residue map

Curated UniProt residues grouped by drug-discovery relevance — catalytic, ligand-binding, modification, and mutation-validated positions. Source: UniProtKB sequence features.

Catalytic / active sites (1): 148 (proton acceptor)

Ligand- & substrate-binding residues (2): 31–39; 54

Post-translational modifications (1): 197

Mutagenesis-validated functional residues (1):

Position	Phenotype
54	loss of kinase activity.

Function

Pathways and Gene Ontology

Reactome pathways

0 pathways

MSigDB gene sets: 68 (showing top): RRAGTTGT_UNKNOWN, GOCC_SECRETORY_GRANULE, LFA1_Q6, GOBP_POSITIVE_REGULATION_OF_CREB_TRANSCRIPTION_FACTOR_ACTIVITY, GOBP_MALE_GAMETE_GENERATION, chr14q12, GOBP_POSITIVE_REGULATION_OF_MOLECULAR_FUNCTION, GOBP_CILIUM_MOVEMENT, GOBP_CILIUM_OR_FLAGELLUM_DEPENDENT_CELL_MOTILITY, GOBP_CELLULAR_PROCESS_INVOLVED_IN_REPRODUCTION_IN_MULTICELLULAR_ORGANISM, GOBP_POSITIVE_REGULATION_OF_DNA_BINDING_TRANSCRIPTION_FACTOR_ACTIVITY, GOBP_DEVELOPMENTAL_PROCESS_INVOLVED_IN_REPRODUCTION, GOBP_FERTILIZATION, GOCC_SECRETORY_VESICLE, GOCC_MOTILE_CILIUM

GO Biological Process (8): protein phosphorylation (GO:0006468), spermatid development (GO:0007286), fertilization (GO:0009566), flagellated sperm motility (GO:0030317), obsolete positive regulation of CREB transcription factor activity (GO:0032793), spermatogenesis (GO:0007283), cell differentiation (GO:0030154), cell division (GO:0051301)

GO Molecular Function (13): magnesium ion binding (GO:0000287), protein serine/threonine kinase activity (GO:0004674), ATP binding (GO:0005524), protein homodimerization activity (GO:0042803), protein-containing complex binding (GO:0044877), protein serine kinase activity (GO:0106310), nucleotide binding (GO:0000166), protein kinase activity (GO:0004672), protein binding (GO:0005515), kinase activity (GO:0016301), transferase activity (GO:0016740), identical protein binding (GO:0042802), metal ion binding (GO:0046872)

GO Cellular Component (7): acrosomal vesicle (GO:0001669), sperm flagellum (GO:0036126), spindle (GO:0005819), cilium (GO:0005929), cytoplasmic vesicle (GO:0031410), motile cilium (GO:0031514), cell projection (GO:0042995)

GO top-level categories

Rollup of top GO terms by namespace:

Category	Terms
protein kinase activity	2
binding	2
phosphorylation	1
protein modification process	1
germ cell development	1
spermatid differentiation	1
sexual reproduction	1
reproductive process	1
cilium-dependent cell motility	1
cilium movement involved in cell motility	1
sperm motility	1
developmental process involved in reproduction	1
male gamete generation	1
cellular developmental process	1
cellular process	1
metal ion binding	1
adenyl ribonucleotide binding	1
purine ribonucleoside triphosphate binding	1
identical protein binding	1
protein dimerization activity	1
nucleoside phosphate binding	1
heterocyclic compound binding	1
kinase activity	1
phosphotransferase activity, alcohol group as acceptor	1
catalytic activity, acting on a protein	1
transferase activity, transferring phosphorus-containing groups	1
catalytic activity	1
protein binding	1
cation binding	1
secretory granule	1
9+2 motile cilium	1
microtubule cytoskeleton	1
intracellular membraneless organelle	1
intraciliary transport particle	1
membrane-bounded organelle	1
plasma membrane bounded cell projection	1
cytoplasm	1
intracellular vesicle	1
cilium	1
cellular anatomical structure	1

Protein interactions and networks

STRING

1567 interactions, top by confidence (×1000):

Protein A	Protein B	Partner UniProt	Score
TSSK4	TSKS	Q9UJT2	719
TSSK4	CREB1	P16220	695
TSSK4	CALY	Q9NYX4	658
TSSK4	CABYR	O75952	618
TSSK4	ROPN1	Q9HAT0	608
TSSK4	SSMEM1	Q8WWF3	608
TSSK4	SPATA6	Q9NWH7	607
TSSK4	SPACA1	Q9HBV2	578
TSSK4	QRICH1	Q2TAL8	560
TSSK4	PRSS55	Q6UWB4	558
TSSK4	QRICH2	Q9H0J4	544
TSSK4	GAPDHS	O14556	528
TSSK4	AKAP4	Q5JQC9	526
TSSK4	KLHL10	Q6JEL2	520
TSSK4	CIB4	A0PJX0	519

IntAct

7 interactions, top by confidence:

A	B	Type	Score
TSSK4	CREB1	psi-mi:“MI:0915”(physical association)	0.690
CREB1	TSSK4	psi-mi:“MI:0915”(physical association)	0.690
CREB1	TSSK4	psi-mi:“MI:0217”(phosphorylation reaction)	0.690
TSSK4	ACACB	psi-mi:“MI:0914”(association)	0.350

BioGRID (8): TSSK4 (Affinity Capture-MS), TSSK4 (Affinity Capture-MS), H2AFX (Affinity Capture-MS), WDR3 (Affinity Capture-MS), ACACB (Affinity Capture-MS), HIST1H2AG (Affinity Capture-MS), HIST2H3PS2 (Affinity Capture-MS), TSSK4 (Two-hybrid)

ESM2 similar proteins: A0A1B5KW97, A0A5B9GBF0, A1CPG7, A1D2C9, A1IVT7, A2BD05, A2QRF6, A3EZ55, B0XR80, D3ZBE5, G1XJZ4, G4N0Z0, G5EDF7, G5EFM9, M1T7M3, O09110, P0C431, P40417, P46734, P52564, P59895, P70236, Q09892, Q0D0P5, Q0U4L8, Q1DUU8, Q1KTF2, Q2H332, Q2WFL5, Q2WGK3, Q4PC06, Q4W6D3, Q4WSF6, Q52PH6, Q5E9X2, Q6PWX2, Q6SA08, Q6XKY3, Q75Q66, Q875L0

Diamond homologs: B5DFG1, D6WMX4, E0W1I1, F4IRW0, O64812, P04413, P06803, P42687, Q01389, Q09013, Q09298, Q0KHV6, Q0VD22, Q2VWQ3, Q4V7Q6, Q4WHP3, Q54IF2, Q5BBL3, Q62070, Q6C7U0, Q6SA08, Q75LR7, Q75V57, Q7RZD3, Q7T6Y1, Q8C1R0, Q99MQ3, Q9BXM7, Q9D411, Q9HFF4, A0AAR7, A1Z9X0, A8WRV1, B5X4Z9, F1MH24, F1SPM8, G5ECQ3, O14976, O15021, O35942

SIGNOR signaling

1 interactions.

A	Effect	B	Mechanism
TSSK4	up-regulates	CREB1	phosphorylation

Disease & clinical

Clinical variants and AI predictions

ClinVar

40 variants total. Per-class counts are floors (≥ shown; pagination cap):

Classification	Count (floor)
Pathogenic	0
Likely pathogenic	0
Uncertain significance	33
Likely benign	4
Benign	0

Top pathogenic / likely-pathogenic (0)

SpliceAI

666 predictions. Top by Δscore:

Variant	Effect	Δscore
14:24207236:GCCT:G	donor_gain	0.9800
14:24207245:T:TA	donor_gain	0.9800
14:24207465:G:GT	donor_gain	0.9800
14:24206500:T:TA	acceptor_gain	0.9700
14:24206503:GGTCA:G	acceptor_loss	0.9700
14:24206505:TCA:T	acceptor_loss	0.9700
14:24206506:CAGG:C	acceptor_loss	0.9700
14:24206507:A:G	acceptor_loss	0.9700
14:24206661:C:T	donor_gain	0.9700
14:24206720:ACCGG:A	donor_loss	0.9700
14:24206722:CGGT:C	donor_loss	0.9700
14:24206723:GGTGA:G	donor_loss	0.9700
14:24206724:G:C	donor_loss	0.9700
14:24206725:T:TC	donor_loss	0.9700
14:24206765:G:GT	donor_gain	0.9700
14:24207481:C:G	donor_gain	0.9700
14:24207962:A:AG	acceptor_gain	0.9700
14:24207963:G:GG	acceptor_gain	0.9700
14:24206501:G:A	acceptor_gain	0.9600
14:24206726:G:GG	donor_loss	0.9600
14:24206724:G:GG	donor_gain	0.9500
14:24206729:G:GT	donor_gain	0.9400
14:24207958:CTCTA:C	acceptor_loss	0.9400
14:24207959:TCTA:T	acceptor_loss	0.9400
14:24207960:CTA:C	acceptor_loss	0.9400
14:24207961:TAG:T	acceptor_loss	0.9400
14:24207962:A:AC	acceptor_loss	0.9400
14:24207963:G:GC	acceptor_loss	0.9400
14:24207246:T:TA	donor_gain	0.9200
14:24207323:CCCAG:C	acceptor_gain	0.9200

AlphaMissense

2219 scored. Top likely-pathogenic:

Variant	Protein change	am_pathogenicity
14:24206085:G:C	K54N	0.999
14:24206085:G:T	K54N	0.999
14:24206723:G:C	R147P	0.999
14:24207148:A:C	D148A	0.999
14:24207148:A:T	D148V	0.999
14:24207202:A:C	D166A	0.999
14:24207202:A:T	D166V	0.999
14:24207203:C:A	D166E	0.999
14:24207203:C:G	D166E	0.999
14:24206081:T:A	V53D	0.998
14:24206128:T:C	F69L	0.998
14:24206130:C:A	F69L	0.998
14:24206130:C:G	F69L	0.998
14:24207202:A:G	D166G	0.998
14:24207323:C:G	C206W	0.998
14:24207420:T:C	F239L	0.998
14:24207422:T:A	F239L	0.998
14:24207422:T:G	F239L	0.998
14:24206033:G:A	G37E	0.997
14:24206078:C:A	A52E	0.997
14:24206083:A:G	K54E	0.997
14:24207148:A:G	D148G	0.997
14:24207149:C:A	D148E	0.997
14:24207149:C:G	D148E	0.997
14:24207201:G:C	D166H	0.997
14:24207366:G:C	D221H	0.997
14:24207367:A:C	D221A	0.997
14:24207372:T:A	W223R	0.997
14:24207372:T:C	W223R	0.997
14:24207418:C:A	P238H	0.997

dbSNP variants (sampled 300 via entrez): RS1000661628 (14:24205644 T>C), RS1000730648 (14:24207257 T>C), RS1000813099 (14:24205547 C>G), RS1001339053 (14:24208738 A>C,G), RS1001487624 (14:24204831 G>A), RS1003277299 (14:24203966 A>C), RS1003543761 (14:24206748 G>A), RS1003946871 (14:24206453 G>A), RS1004693620 (14:24205212 T>C), RS1004898159 (14:24207913 G>C), RS1005575173 (14:24204311 G>C), RS1006243591 (14:24207676 G>A), RS1006294363 (14:24208066 C>G,T), RS1006907503 (14:24204970 C>T), RS1007033438 (14:24204758 A>C)

Disease associations

OMIM: gene MIM:610711 | disease phenotypes:

GenCC curated gene-disease

Mondo (0):

Orphanet (0):

HPO phenotypes

0 total (0 of 0 shown, HPO-id order):

GWAS associations

0 associations (top):

Drugs & pharmacology

Drug and pharmacology data

Is drug target: yes

ChEMBL targets (1): CHEMBL4295868 (SINGLE PROTEIN)

PharmGKB: 1 entry (VIP=true, CPIC=false)

GtoPdb / IUPHAR curated pharmacology

(IUPHAR/BPS Guide to Pharmacology — expert-curated)

Target class: enzyme — Testis specific kinase (TSSK) family

CTD chemical–gene interactions

7 total (human), top 7 by PubMed support.

Chemical	Actions (top 5)	PubMed papers
aristolochic acid I	increases expression	1
S-(1,2-dichlorovinyl)cysteine	affects cotreatment, increases expression	1
di-n-butylphosphoric acid	affects expression	1
Endosulfan	decreases expression	1
Formaldehyde	increases expression	1
Lipopolysaccharides	affects cotreatment, increases expression	1
Quercetin	increases expression	1

ChEMBL screening assays

25 unique, capped per target: 25 binding

Representative assays (with source publication via chembl_document):

Assay ID	Type	Description	Source paper
CHEMBL4191222	Binding	Inhibition of recombinant full-length human TSSK4 at 1 uM using KKLNRTLSFAEPG as substrate after 40 mins in presence of [gamma-33P]ATP by scintillation counting method	Discovery of pyrazolopyrimidine derivatives as novel inhibitors of ataxia telangiectasia and rad3 related protein (ATR). — Bioorg Med Chem Lett

Cellosaurus cell lines

3 cell lines: 3 cancer cell line

First 10 cell lines (id-ordered, not curated):

Cellosaurus	Name	Category	Sex
CVCL_B2JW	Abcam HeLa TSSK4 KO	Cancer cell line	Female
CVCL_TV01	HAP1 TSSK4 (-) 1	Cancer cell line	Male
CVCL_TV02	HAP1 TSSK4 (-) 2	Cancer cell line	Male

Clinical trials (associated diseases)

0 trials via MONDO — disease-level, not drug-specific.