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PMID: 4009696 Published · ppublish English Journal Article Research Support, U.S. Gov't, P.H.S.

Proteolysis of cardiac gap junctions during their isolation from rat hearts.

The Journal of membrane biology ·Vol. 85 ·No. 2 ·1985-00-00 ·Pages 159-68

Manjunath CK, Goings GE, Page E

Abstract

Gap junctions (GJ) isolated from rat hearts in presence of the protease inhibitor phenylmethylsulfonylfluoride (PMSF) contain a Mr 44,000 to 47,000 major polypeptide and have a urea-resistant layer of fuzz on their cytoplasmic surfaces, whereas junctions isolated without PMSF are proteolyzed to a Mr 29,500 polypeptide by a serine protease and have smooth cytoplasmic surfaces (C.K. Manjunath, G.E. Goings & E. Page Am. J. Physiol. 246:H865-H875, 1984). Rat liver GJ isolated with or without PMSF contain a Mr 28,000 polypeptide and have smooth cytoplasmic surfaces. Here we examine the origin, type and inhibitor sensitivity of the heart protease; why similar proteolysis is absent during isolation of rat liver gap junctions; and whether the Mr 44,000 to 47,000 cardiac GJ polypeptide is the precursor of the Mr 29,500 subunit. We show that the Mr 44,000 to 47,000 polypeptide corresponds to the unproteolyzed connexon subunit; that proteolysis of this polypeptide occurs predominantly during exposure to high ionic strength solution (0.6 M KI) which releases serine protease from mast cell granules; that this protease is inhibitable with PMSF and (less completely) soybean trypsin inhibitor and chymostatin; and that in vivo degranulation of mast cells by injecting rats with compound 48/80 fails to prevent breakdown of cardiac GJ during isolation. The results support the concept that GJ from rat heart and liver differ in protein composition.

MeSH Terms
Animals Cell Fractionation Cell Membrane/ultrastructure Female Intercellular Junctions/ultrastructure Liver/ultrastructure Male Mast Cells/ultrastructure Membrane Proteins/metabolism Microscopy, Electron Myocardium/ultrastructure Organ Specificity Phenylmethylsulfonyl Fluoride/pharmacology Rats Rats, Inbred Strains
Chemicals
Membrane Proteins Phenylmethylsulfonyl Fluoride
Authors & Affiliations
3 authors, click to expand affiliations / ORCID
Manjunath C K
Goings G E
Page E
References (33)
33 references, click to expand
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Article Info
Journal
The Journal of membrane biology
Abbr.
J Membr Biol
ISSN
0022-2631
DOI
10.1007/BF01871268
Published
1985-00-00
Pages
159-68
Language
English
Region
United States
NLM ID
0211301
Subset
IM
Grants
NHLBI NIH HHS · HL 10503 · United States
NHLBI NIH HHS · HL 20592 · United States
External Links
PubMed source DOI: 10.1007/BF01871268 View journal details
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