Naturally-occurring spinosyn A and its derivatives function as argininosuccinate synthase activator and tumor inhibitor

Jun-Li Luo ,Xiyuan Hu,Yuanzhu Xie,Xiaodan Chen,Zhitian Luo ,Zizheng Zou,Wensong Luo,Zhengnan Ming,Fansen Kong ,Suyou Liu,Ousheng Liu,Ling Chen,Wei Yi ,Na Xu,Li Xia,Jijia Li,Da‐You Ma ,Kunjian Peng,Xuan Li,Min Wen,Chunzhang Yang ,Ceshi Chen,Tiao Luo,Dong‐Sheng Cao

doi:10.1038/s41467-021-22235-8

Abstract

Argininosuccinate synthase (ASS1) is a ubiquitous enzyme in mammals that catalyzes the formation of argininosuccinate from citrulline and aspartate. ASS1 genetic deficiency in patients leads to an autosomal recessive urea cycle disorder citrullinemia, while its somatic silence or down-regulation is very common in various human cancers. Here, we show that ASS1 functions as a tumor suppressor in breast cancer, and the pesticide spinosyn A (SPA) and its derivative LM-2I suppress breast tumor cell proliferation and growth by binding to and activating ASS1. The C13-C14 double bond in SPA and LM-2I while the Cys97 (C97) site in ASS1 are critical for the interaction between ASS1 and SPA or LM-2I. SPA and LM-2I treatment results in significant enhancement of ASS1 enzymatic activity in breast cancer cells, particularly in those cancer cells with low ASS1 expression, leading to reduced pyrimidine synthesis and consequently the inhibition of cancer cell proliferation. Thus, our results establish spinosyn A and its derivative LM-2I as potent ASS1 enzymatic activator and tumor inhibitor, which provides a therapeutic avenue for tumors with low ASS1 expression and for those non-tumor diseases caused by down-regulation of ASS1.

Highlights

Argininosuccinate synthase (ASS1) is a ubiquitous enzyme in mammals that catalyzes the formation of argininosuccinate from citrulline and aspartate
We found that spinosyn A (SPA) had mild effect on immortalized normal human breast epithelial cells while significantly inhibited the proliferation of most breast cancer (BC) cell lines tested in a dose-dependent manner (Fig. 1b, Supplementary Fig. S4a)
The expression of ASS1 is increased in some types of tumors, such as colorectal, ovarian, stomach, and lung cancers, while in most types of cancers, such as melanoma, prostate cancer, breast cancer, bladder cancer, hepatocellular carcinoma, mesothelioma, pancreatic cancer, nasopharyngeal carcinoma, osteosarcomas, and myxofibrosarcomas, the expression of ASS1 is decreased[3,4,5,6]

Summary

Introduction

Argininosuccinate synthase (ASS1) is a ubiquitous enzyme in mammals that catalyzes the formation of argininosuccinate from citrulline and aspartate. A natural substance isolated from Saccharopolyspora spinosa, is the active ingredient in many registered pesticide products and in some drugs regulated by the US Food and Drug Administration (FDA) It is a mixture of two macrocyclic lactone compounds called spinosyn A (SPA) and spinosyn D14. It has been reported that the highly selective toxicity to insects may be related to its indirect interaction with acetylcholine receptor and gammaaminobutyric acid (GABA) receptor of insect central nervous system[20,21] This may not apply to mammals as it has little or low toxicity to mammals, suggesting that spinosad may function differently in mammalian cells[14,15,16]. SPA and its derivative LM-2I target and bind to ASS1 at the 97th cysteine site in tumor cells, leading to significantly enhanced ASS1 enzymatic activity and tumor inhibitory effect

Methods

Results

Conclusion