rs4807015 — PTPRS PTPRS T2D risk variant

PTPRS rs4807015 — An Intronic Variant That Elevates Diabetes Risk in Both Sexes

The PTPRS gene encodes receptor protein tyrosine phosphatase sigma (RPTPσ)¹¹ receptor protein tyrosine phosphatase sigma (RPTPσ)
A cell-surface enzyme that belongs to the LAR subfamily of receptor-type phosphatases. It has an extracellular ligand-binding domain and two intracellular catalytic domains, one active and one regulatory, located on chromosome 19p13.3. RPTPσ functions as a negative regulator of tyrosine-kinase-based signalling by removing phosphate groups from tyrosine residues on target proteins. Two of the most important targets in the context of glucose metabolism are the insulin receptor itself and insulin receptor substrate proteins (IRS-1 and IRS-2)²² insulin receptor substrate proteins (IRS-1 and IRS-2)
Adaptor proteins that relay the insulin receptor's signal into the cell's interior; when dephosphorylated by PTPs such as RPTPσ, the downstream signalling cascade is attenuated and insulin sensitivity is reduced.

rs4807015 is an intronic variant — it sits within an intron of PTPRS and does not change any amino acid in the protein. The PTPRS gene is transcribed from the minus strand of chromosome 19, so the genomic (plus-strand) reference allele is T, with C as the alternate allele. The C allele is the risk allele identified in the discovery cohort; it likely acts as a haplotype tag — travelling on the same chromosomal segment as one or more functional changes elsewhere in the gene that upregulate RPTPσ expression or activity.

The Mechanism

Two lines of experimental evidence connect elevated RPTPσ activity to impaired glucose homeostasis. First, in pancreatic beta cells³³ beta cells
The insulin-secreting cells of the pancreatic islets of Langerhans; their capacity to release insulin in response to rising blood glucose is central to preventing type 2 diabetes, RPTPσ dephosphorylates proteins that mediate insulin granule exocytosis, reducing the efficiency of glucose-stimulated insulin secretion. The Goto-Kakizaki spontaneously diabetic rat model shows approximately 60% overexpression of PTP sigma in islets and liver compared with normoglycaemic controls; treating isolated GK islets with antisense oligonucleotides targeting PTP sigma restored glucose-induced insulin secretion to near-normal levels, establishing a direct causal link.

Second, mice lacking PTPRS entirely (RPTPσ knockout mice) display reduced fasting plasma glucose and insulin⁴⁴ reduced fasting plasma glucose and insulin
Chagnon et al. 2006, Canadian Journal of Physiology and Pharmacology — RPTPσ-/- mice showed significantly lower fasting glucose and insulin and enhanced whole-body insulin sensitivity on insulin tolerance testing, consistent with the hypothesis that higher phosphatase activity constrains insulin action in vivo. More recently, pharmacological inhibition of PTPRS and related phosphatases in differentiated muscle cells was shown to increase cellular glucose uptake, pointing toward PTPRS as an actionable target in insulin-resistant tissues.

Epigenetic profiling of islets from pre-diabetic mouse models ranked PTPRS among the strongest predictors of future T2D (area under ROC curve 0.62–0.73), indicating that changes in PTPRS expression at the epigenetic level precede clinical disease onset — consistent with the gene being functionally upstream of the metabolic decline.

The Evidence

The primary human evidence comes from a Swedish Caucasian cohort⁵⁵ Swedish Caucasian cohort
Långberg et al. 2007, European Journal of Endocrinology — 497 subjects with normal glucose tolerance (NGT), 262 with impaired glucose tolerance (IGT), and 298 patients with T2D; all Swedish Caucasians; three PTPRS SNPs tested (n=1,057 total). Among three PTPRS variants tested, rs4807015 was associated with T2D with an odds ratio of 1.74 (p=0.029) across both sexes in logistic regression — the highest sex-combined effect size of the three variants in the study. This is one of the larger effect sizes reported for a common intronic variant in this category; for comparison, the well-replicated TCF7L2 rs7903146 T2D variant typically shows ORs of 1.35–1.45 in European cohorts. The limitation is that this association has not been formally replicated in independent large-scale GWAS data, and the discovery cohort of ~300 T2D cases has limited statistical power. The evidence level is accordingly classified as moderate.

Practical Actions

The C allele is nearly balanced with T in European populations (~48% vs 52%), meaning approximately one in four Europeans is CC homozygous. The actionable concern is that elevated RPTPσ activity attenuates insulin signalling in both beta cells and insulin-sensitive tissues. Interventions that reduce the secretory and metabolic burden — glycaemic load reduction, periodic cardiometabolic monitoring, and proactive fasting insulin testing — are most directly supported by the mechanistic model.

Interactions

PTPRS harbours two other variants associated with T2D in the same Swedish cohort: rs1143699 (synonymous, OR=1.57, strongest in men) and rs1978237 (intronic, OR=1.59, both sexes). All three may tag the same risk haplotype across the PTPRS locus, in which case their effects are not additive. Formal haplotype analysis has not been published. Users carrying risk alleles at multiple PTPRS variants may not face proportionally higher risk, but the co-occurrence strengthens the plausibility of a high-expression PTPRS haplotype.