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Defective binding of SPINK1 variants is an uncommon mechanism for impaired trypsin inhibition in chronic pancreatitis.

ABSTRACT: The serine protease inhibitor Kazal type 1 (SPINK1) protects the pancreas from intrapancreatic trypsin activation that can lead to pancreatitis. Loss-of-function genetic variants of SPINK1 increase the risk for chronic pancreatitis, often by diminishing inhibitor expression or secretion. Variants that are secreted normally have been presumed to be pathogenic because of defective trypsin inhibition, but evidence has been lacking. Here, we report quantitative studies on the inhibition of human trypsins by wildtype SPINK1 and seven secreted missense variants. We found that tyrosine sulfation of human trypsins weakens binding of SPINK1 because of altered interactions with Tyr43 in the SPINK1 reactive loop. Using authentic sulfated human trypsins, we provide conclusive evidence that SPINK1 variants N34S, N37S, R65Q, and Q68R have unimpaired inhibitory activity, whereas variant P55S exhibits a small and clinically insignificant binding defect. In contrast, rare variants K41N and I42M that affect the reactive-site peptide bond of SPINK1 decrease inhibitor binding by 20,000- to 30,000-fold and three- to sevenfold, respectively. Taken together, the observations indicate that defective trypsin inhibition by SPINK1 variants is an uncommon mechanism in chronic pancreatitis. The results also strengthen the notion that a decline in inhibitor levels explains pancreatitis risk associated with the large majority of SPINK1 variants.

SUBMITTER: Szabo A

PROVIDER: S-EPMC7949130 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Functional significance of SPINK1 promoter variants in chronic pancreatitis.

Project description:Chronic pancreatitis is a progressive inflammatory disorder of the pancreas, which often develops as a result of genetic predisposition. Some of the most frequently identified risk factors affect the serine protease inhibitor Kazal type 1 (SPINK1) gene, which encodes a trypsin inhibitor responsible for protecting the pancreas from premature trypsinogen activation. Recent genetic and functional studies indicated that promoter variants in the SPINK1 gene might contribute to disease risk in carriers. Here, we investigated the functional effects of 17 SPINK1 promoter variants using luciferase reporter gene expression assay in four different cell lines, including three pancreatic acinar cell lines (rat AR42J with or without dexamethasone-induced differentiation and mouse 266-6) and human embryonic kidney 293T cells. We found that most variants caused relatively small changes in promoter activity. Surprisingly, however, we observed significant variations in the effects of the promoter variants in the different cell lines. Only four variants exhibited consistently reduced promoter activity in all acinar cell lines, confirming previous reports that variants c.-108G>T, c.-142T>C, and c.-147A>G are risk factors for chronic pancreatitis and identifying c.-52G>T as a novel risk variant. In contrast, variant c.-215G>A, which is linked with the disease-associated splice-site mutation c.194 + 2T>C, caused increased promoter activity, which may mitigate the overall effect of the pathogenic haplotype. Our study lends further support to the notion that sequence evaluation of the SPINK1 promoter region in patients with chronic pancreatitis is justified as part of the etiological investigation.

| S-EPMC4421017 | biostudies-literature

Signal peptide variants that impair secretion of pancreatic secretory trypsin inhibitor (SPINK1) cause autosomal dominant hereditary pancreatitis.

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| S-EPMC2765331 | biostudies-literature

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| S-EPMC7704661 | biostudies-literature

Bicarbonate defective CFTR variants increase risk for chronic pancreatitis: A meta-analysis.

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| S-EPMC9584382 | biostudies-literature

Pancreatic Secretory Trypsin Inhibitor (SPINK1) Gene Mutation in Patients with Acute Alcohol Pancreatitis (AAP) Compared to Healthy Controls and Heavy Alcohol Users without Pancreatitis.

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PRSS1, SPINK1, CFTR, and CTRC Pathogenic Variants in Korean Patients With Idiopathic Pancreatitis.

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| S-EPMC5011109 | biostudies-literature

Association of rare SPINK1 gene mutation with another base substitution in chronic pancreatitis patients.

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| S-EPMC4088203 | biostudies-literature

Progression of Recurrent Pancreatitis to Chronic Pancreatitis within 3 Years due to <i>SPINK1</i> Mutation IVS3+2T>C.

Project description:When the etiology of pancreatitis cannot be determined despite sufficient investigation, recurrence and progression to chronic pancreatitis often involve genetic mutations. Herein, we describe a case of recurrent pancreatitis with the IVS3+2T>C mutation in the serine protease inhibitor Kazal type 1 (SPINK1) gene that progressed to chronic pancreatitis in only 3 years. A 35-year-old man was referred to our hospital, where he was diagnosed with mild pancreatitis and was treated conservatively. However, the patient experienced recurrent episodes of pancreatitis, which progressed to become chronic pancreatitis with a pancreatic calcification 1 year later. After 3 years, the patient developed pancreatic duct stenosis and required a pancreatic duct stent placement. Regarding the cause of chronic pancreatitis, alcohol abuse was ruled out based on history taking. Considering the course of treatment, autoimmune pancreatitis and obstructive pancreatitis, such as pancreatic divisum, were also ruled out. Finally, a germline genetic test was performed to determine the etiology of pancreatitis, which revealed the IVS3+2T>C mutation in SPINK1. This case shows the importance of genetic testing in patients with idiopathic pancreatitis to determine their etiology and is a rare incident that can report the progression of the disease from acute to chronic pancreatitis.

| S-EPMC9891844 | biostudies-literature

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