Human α-defensin regulates smooth muscle cell contraction: A role for low-density lipoprotein receptor-related protein/α2-macroglobulin receptor

Taher Nassar, Sa'ed Akkawi, Rachel Bar-Shavit, Abdullah Haj-Yehia, Khalil Bdeir, Abu Bakr Al-Mehdi, Mark Tarshis, Abd Al Roof Higazi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

87 Scopus citations

Abstract

We have previously identified α-defensin in association with medial smooth muscle cells (SMCs) in human coronary arteries. In the present paper we report that α-defensin, at concentrations below those found in pathological conditions, inhibits phenylephrine (PE)-induced contraction of rat aortic rings. Addition of 1 μM α-defensin increased the half-maximal effective concentration (EC50) of PE on denuded aortic rings from 32 to 630 nM. The effect of α-defensin was dose dependent and saturable, with a half-maximal effect at 1 μM. α-Defensin binds to human umbilical vein SMCs in a specific manner. The presence of 1 μM α-defensin inhibited the PE-mediated Ca++ mobilization in SMCs by more than 80%. The inhibitory effect of α-defensin on contraction of aortic rings and Ca++ mobilization was completely abolished by anti-low-density lipoprotein receptor-related protein/α2-macroglobulin receptor (LRP) antibodies as well as by the antagonist receptor-associated protein (RAP). α-Defensin binds directly to isolated LRP in a specific and dose-dependent manner; the binding was inhibited by RAP as well as by anti-LRP antibodies. α-Defensin is internalized by SMCs and interacts with 2 intracellular subtypes of protein kinase C (PKC) involved in muscle contraction, α and β. RAP and anti-LRP antibodies inhibited the binding and internalization of α-defensin by SMCs and its interaction with intracellular PKCs. These observations suggest that binding of α-defensin to LRP expressed in SMCs leads to its internalization; internalized α-defensin binds to PKC and inhibits its enzymatic activity, leading to decreased Ca++ mobilization and SMC contraction in response to PE.

Original languageAmerican English
Pages (from-to)4026-4032
Number of pages7
JournalBlood
Volume100
Issue number12
DOIs
StatePublished - 1 Dec 2002
Externally publishedYes

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