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Microvasc Res. 2014 Sep;95:94-102. doi: 10.1016/j.mvr.2014.07.007. Epub 2014 Jul 27.

Proline-rich region of non-muscle myosin light chain kinase modulates kinase activity and endothelial cytoskeletal dynamics.

Author information

1
Division of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois Hospital and Health Science System, Chicago, IL, USA.
2
University of Arizona Health Sciences Center, Tucson, AZ, USA.
3
Division of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois Hospital and Health Science System, Chicago, IL, USA. Electronic address: sdudek@uic.edu.

Abstract

Disruption of the pulmonary endothelial barrier and subsequent vascular leak is a hallmark of acute lung injury. Dynamic rearrangements in the endothelial cell (EC) peripheral membrane and underlying cytoskeleton are critical determinants of barrier function. The cytoskeletal effector protein non-muscle myosin light chain kinase (nmMLCK) and the actin-binding regulatory protein cortactin are important regulators of the endothelial barrier. In the present study we functionally characterize a proline-rich region of nmMLCK previously identified as the possible site of interaction between nmMLCK and cortactin. A mutant nmMLCK construct deficient in proline residues at the putative sites of cortactin binding (amino acids 973, 976, 1019, 1022) was generated. Co-immunoprecipitation studies in human lung EC transfected with wild-type or mutant nmMLCK demonstrated similar levels of cortactin interaction at baseline and after stimulation with the barrier-enhancing agonist, sphingosine 1-phosphate (S1P). In contrast, binding studies utilizing recombinant nmMLCK fragments containing the wild-type or proline-deficient sequence demonstrated a two-fold increase in cortactin binding (p<0.01) to the mutant construct. Immunofluorescent microscopy revealed an increased stress fiber density in ECs expressing GFP-labeled mutant nmMLCK at baseline (p=0.02) and after thrombin (p=0.01) or S1P (p=0.02) when compared to wild-type. Mutant nmMLCK demonstrated an increase in kinase activity in response to thrombin (p<0.01). Kymographic analysis demonstrated an increased EC membrane retraction distance and velocity (p<0.01) in response to the barrier disrupting agent thrombin in cells expressing the mutant vs. the wild-type nmMLCK construct. These results provide evidence that critical prolines within nmMLCK (amino acids 973, 976, 1019, 1022) regulate cytoskeletal and membrane events associated with pulmonary endothelial barrier function.

KEYWORDS:

ARDS; Barrier function; Cortactin; Cytoskeleton; Endothelium; Membrane dynamics; Non-muscle myosin light chain kinase; Stress fibers

PMID:
25072537
PMCID:
PMC4188692
DOI:
10.1016/j.mvr.2014.07.007
[Indexed for MEDLINE]
Free PMC Article
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