Elevations in plasma homocysteine levels are associated with an increased risk of a number of human diseases including vascular disease, neural tube defects, age-related dementia, and osteoporoticfractures. Homocysteine can be metabolized by the action of cystathionine (3-synthase (CBS) which condenses homocysteine with serine to form cystathionine. Individuals lacking functional CBS due to mutation have clinical CBS deficiency that is characterized by extremely elevated plasma homocysteine levels and phenotypes in the vascular, nervous, skeletal and visual systems. Some CBS-deficient patients respond clinically to pharmacologic doses of pyridoxine (vitamin B6). Most mutations in CBS are point mutations resulting in single amino acid substitutions in the CBS protein. We have previously shown that it is possible to restore function to a large percentage of mutant CBS proteins by truncating the C-terminal domain of CBS or by having specific missense mutations within this domain. More recently, we have found that chemical chaperones can also restore enzyme activity to mutant CBS proteins. The overall goal of this application is to modulate the activity of mutant CBSenzymes by chemical and genetic means. There are four specific aims. First, we will determine the mechanism by which chemical chaperones restore function to mutant CBS proteins. We will determine the number of different mutant CBS proteins that can be rescued by chemical chaperone treatment and we will determine how these treatments affect CBS function. We will also attempt to identify chaperone proteins whose overexpression can stabilize mutant CBS. In our second aim, we will identify and characterize new small molecules that can activate mutant CBS enzymes using a high- throughput screening strategy in S. cerevisiae. In our third aim, we will develop a mouse model to study pyridoxine-responsive homocystinuria. This will be done by making a transgenic mouse expressing the R266K mutant form of CBS and crossing this animal with a CBS knockout mouse. In the fourth aim, we will develop mouse models to study the effects of mutations in the regulatory domain of CBS. Two different mice will be characterized, one with a deletion in the regulatory domain of CBS and the other with a missense mutation in this domain. These studies may lead to new strategies to treat CBS-deficiency and other homocysteine related diseases. Lay abstract: Elevated plasma homocysteine is associated with a number of human diseases. Cystathionine beta-synthase (CBS) is a key enzyme in the metabolism of homocysteine. In this proposal we will develop new strategies and reagents to activate CBS thereby reducing plasma homocysteine levels.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-GTIE (01))
Program Officer
Ershow, Abby
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Fox Chase Cancer Center
United States
Zip Code
Lee, Hyung-Ok; Wang, Liqun; Kuo, Yin-Ming et al. (2017) Lack of global epigenetic methylation defects in CBS deficient mice. J Inherit Metab Dis 40:113-120
Gupta, Sapna; Wang, Liqun; Anderl, Janet et al. (2013) Correction of cystathionine ?-synthase deficiency in mice by treatment with proteasome inhibitors. Hum Mutat 34:1085-93
Zhang, Daqing; Fang, Pu; Jiang, Xiaohua et al. (2012) Severe hyperhomocysteinemia promotes bone marrow-derived and resident inflammatory monocyte differentiation and atherosclerosis in LDLr/CBS-deficient mice. Circ Res 111:37-49
Cheng, Zhongjian; Jiang, Xiaohua; Kruger, Warren D et al. (2011) Hyperhomocysteinemia impairs endothelium-derived hyperpolarizing factor-mediated vasorelaxation in transgenic cystathionine beta synthase-deficient mice. Blood 118:1998-2006
Wei, Qiong; Wang, Liqun; Wang, Qiang et al. (2010) Testing computational prediction of missense mutation phenotypes: functional characterization of 204 mutations of human cystathionine beta synthase. Proteins 78:2058-74
Singh, Laishram R; Gupta, Sapna; Honig, Nicholaas H et al. (2010) Activation of mutant enzyme function in vivo by proteasome inhibitors and treatments that induce Hsp70. PLoS Genet 6:e1000807
Tang, Baiqing; Mustafa, Aladdin; Gupta, Sapna et al. (2010) Methionine-deficient diet induces post-transcriptional downregulation of cystathionine ýý-synthase. Nutrition 26:1170-5
Singh, Laishram R; Kruger, Warren D (2009) Functional rescue of mutant human cystathionine beta-synthase by manipulation of Hsp26 and Hsp70 levels in Saccharomyces cerevisiae. J Biol Chem 284:4238-45
Zhang, Daqing; Jiang, Xiaohua; Fang, Pu et al. (2009) Hyperhomocysteinemia promotes inflammatory monocyte generation and accelerates atherosclerosis in transgenic cystathionine beta-synthase-deficient mice. Circulation 120:1893-902
Kadariya, Yuwaraj; Yin, Bu; Tang, Baiqing et al. (2009) Mice heterozygous for germ-line mutations in methylthioadenosine phosphorylase (MTAP) die prematurely of T-cell lymphoma. Cancer Res 69:5961-9

Showing the most recent 10 out of 13 publications