Cirrhosis is the advanced stage in the spectrum of liver injury and portends a poor prognosis. An early and important step in the development of cirrhosis is the conversion of extracellular, soluble fibronectin (FN) into an insoluble matrix-bound constituent by the biomechanical actions of the integrin family of proteins on the plasma membrane of hepatic stellate cells (HSC). This conversion is important because it accelerates the subsequent steps of collagen matrix deposition that typify cirrhosis. Our preliminary data demonstrate that protein levels of the proteoglycan neuropilin-1 (NRP) are increased in both humans and animals with alcohol and non-alcohol induced liver fibrosis and promotes FN matrix assembly. Mechanistically, we show that FN binding with NRP promotes ???? integrin dependent generation of matrix-bound FN. FN binding with NRP is also associated with increased binding of FN with ???? and with activation of a key intracellular trafficking protein, c abl. These important initial observations have stimulated us to propose the central hypothesis that NRP promotes ???? integrin dependent FN matrix assembly in liver fibrosis by a dual mechanism that involves both increased FN binding with ???? and increased c-abl mediated plasma membrane enrichment of ????. To examine our hypothesis, we propose the following Specific Aims: 1) NRP enhances FN interaction with ???? integrin thereby promoting ???? activity and assembly of matrix-bound FN. In Subaim 1a, we will determine how specific proteoglycan modifications and ligand binding domains of NRP promote its binding with FN. In Subaim 1b, we will examine the mechanism by which NRP binding with FN increases binding of FN with ????, thereby promoting ???? mediated assembly of FN matrix. 2) NRP activation of c-abl increases membrane redistribution of ???? thereby further promoting FN matrix assembly. In Subaim 2a, we will ascertain how NRP activates c-abl. In Subaim 2b, we will identify how NRP activated c-abl promotes ???? integrin redistribution to the plasma membrane and increased FN matrix assembly. 3) NRP promotes FN assembly and ensuing liver fibrosis in vivo. In this Aim, we will use a compliment of genetically modified mice that lack NRP, ?1 integrin, or c-abl in HSC, in combination with molecular interventions that ascertain NRP structure- function relationships to determine how NRP inhibition in vivo prevents alcohol and non-alcohol induced generation of FN matrix and liver fibrosis. Thus, Aims 1 and 2 will focus on how NRP regulates integrin function both as an extracellular "co-receptor", and as a regulator of integrin plasma membrane targeting, respectively. In turn, Aim 3 will focus on in vivo applicability of the finding using state-of-the-art imaging approaches. In total, this proposal, using conceptually and technically innovative approaches will address a novel hypothesis pertaining to an early, reversible, and significant step in the HSC regulation of matrix dynamics that drive the process of liver fibrosis.

Public Health Relevance

Cirrhosis is a leading cause of morbidity and mortality in the US and in the world and therefore better understanding of the mechanisms of liver fibrosis development can lead to important prevention and treatment advances. This study will explore mechanisms that lead to both alcohol and non- alcohol induced fibrosis.

Agency
National Institute of Health (NIH)
Type
Research Project (R01)
Project #
5R01AA021171-03
Application #
8658783
Study Section
Hepatobiliary Pathophysiology Study Section (HBPP)
Program Officer
Gao, Peter
Project Start
Project End
Budget Start
Budget End
Support Year
3
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Mayo Clinic, Rochester
Department
Type
DUNS #
City
Rochester
State
MN
Country
United States
Zip Code
55905
Simonetto, Douglas A; Yang, Hui-yin; Yin, Meng et al. (2015) Chronic passive venous congestion drives hepatic fibrogenesis via sinusoidal thrombosis and mechanical forces. Hepatology 61:648-59
Singal, Ashwani K; Kamath, Patrick S; Gores, Gregory J et al. (2014) Alcoholic hepatitis: current challenges and future directions. Clin Gastroenterol Hepatol 12:555-64; quiz e31-2
Bi, Yan; Li, Jiachu; Ji, Baoan et al. (2014) Sphingosine-1-phosphate mediates a reciprocal signaling pathway between stellate cells and cancer cells that promotes pancreatic cancer growth. Am J Pathol 184:2791-802
Liu, Chunsheng; Li, Jiachu; Xiang, Xiaoyu et al. (2014) PDGF receptor-? promotes TGF-? signaling in hepatic stellate cells via transcriptional and posttranscriptional regulation of TGF-? receptors. Am J Physiol Gastrointest Liver Physiol 307:G749-59
de Assuncao, Thiago M; Lomberk, Gwen; Cao, Sheng et al. (2014) New role for Kruppel-like factor 14 as a transcriptional activator involved in the generation of signaling lipids. J Biol Chem 289:15798-809
Yang, Liu; Kwon, Junghee; Popov, Yury et al. (2014) Vascular endothelial growth factor promotes fibrosis resolution and repair in mice. Gastroenterology 146:1339-50.e1
Bi, Yan; Mukhopadhyay, Dhriti; Drinane, Mary et al. (2014) Endocytosis of collagen by hepatic stellate cells regulates extracellular matrix dynamics. Am J Physiol Cell Physiol 307:C622-33
Singal, Ashwani K; Kamath, Patrick S; Francisco Ziller, Nickie et al. (2013) Nutritional status of patients with alcoholic cirrhosis undergoing liver transplantation: time trends and impact on survival. Transpl Int 26:788-94
Zou, Li; Cao, Sheng; Kang, Ningling et al. (2012) Fibronectin induces endothelial cell migration through *1 integrin and Src-dependent phosphorylation of fibroblast growth factor receptor-1 at tyrosines 653/654 and 766. J Biol Chem 287:7190-202