scholarly journals Regulated secretion of a serine protease that activates an extracellular matrix-degrading metalloprotease during fertilization in Chlamydomonas.

1989 ◽  
Vol 109 (4) ◽  
pp. 1689-1694 ◽  
Author(s):  
W J Snell ◽  
W A Eskue ◽  
M J Buchanan
Keyword(s):  
Extracellular Matrix ◽  
Cell Wall ◽  
Serine Protease ◽  
Cellular Responses ◽  
Cell Contact ◽  
Relative Molecular Mass ◽  
Mating Types ◽  
Dibutyryl Camp ◽  
Sexual Signal ◽  
Regulated Secretion

During fertilization in the biflagellated alga, Chlamydomonas reinhardtii, gametes of opposite mating types adhere to each other via agglutinin molecules located on their flagellar surfaces, generating a sexual signal that induces several cellular responses including cell wall release. This cell contact-generated signal is mediated by cAMP and release of the wall, which is devoid of cellulose and contains several hydroxyproline-rich glycoproteins, is due to the activation of a metalloprotease, lysin. Although we originally assumed that lysin would be stored intracellularly in a compartment structurally separate from its substrate, recently we showed that lysin is stored in the periplasm as an inactive, higher relative molecular mass precursor, prolysin (Buchanan, M.J., S. H. Imam, W. A. Eskue, and W. J. Snell. 1989. J. Cell Biol. 108:199-207). Here we show that conversion of prolysin to lysin is due to a cellular, nonperiplasmic enzyme that has the properties of a serine protease. Release of this serine protease into the periplasm is induced by incubation of gametes in dibutyryl cAMP. This may be one of the few examples of regulated secretion of a protease in a eucaryotic microorganism and a novel example of regulated secretion in a plant system.

scholarly journals The role of intermolecular disulfide bonding in deposition of GP140 in the extracellular matrix.

1984 ◽  
Vol 99 (1) ◽  
pp. 105-114 ◽  
Author(s):  
W G Carter
Keyword(s):  
Extracellular Matrix ◽  
Culture Media ◽  
Molecular Forms ◽  
Cell Protein ◽  
Cell Contact ◽  
Relative Molecular Mass ◽  
Disulfide Bonding ◽  
Sequence Of Events ◽  
The Matrix ◽  
Matrix Precipitation

Human WI-38 fibroblasts in cultures synthesized at least three molecular forms of the major, extracellular matrix glycoprotein (GP), GP140: (a) cytoplasmic GP140 (1.2 ng of GP140/micrograms of cell protein) was detergent-soluble, underglycosylated, and possessed detectable levels of intermolecular disulfide bonding; (b) matrix GP140 (3.6 ng of GP140/micrograms of cell protein) was detergent-insoluble, more highly glycosylated and polymerized by intermolecular disulfide bonding, and co-distributed in the extracellular matrix with fibronectin; and (c) released GP140 (2 ng of GP140/micrograms of cell protein per 24 h) was recovered in the conditioned culture media and lacked intermolecular disulfide bonding. Cytoplasmic GP140 was the immediate biosynthetic precursor of the matrix form of GP140. In addition, various human adult and fetal tissues contained a form of GP140 that resembled the fibroblast matrix GP140 in the degree of intermolecular disulfide bonding, relative molecular mass, and immunological reactivity. Analysis of the sequence of events in assembly of GP140 and fibronectin in the extracellular matrix detected the following: (a) fibronectin was first to appear in the extracellular matrix; (b) GP140 accumulated in the cytoplasm, then deposited in the extracellular matrix and co-aligned with the established fibronectin; and (c) maturation of the extracellular matrix proceeded by continued intermolecular disulfide bonding. To evaluate possible roles for intermolecular disulfide bonding in cell interactions, a unique assay system was utilized based on the ability of labeled cells to incorporate radioactive matrix components into a biotinylated exogenous matrix. Precipitation of the biotinylated matrix from extracts of the cultures using avidin indicated: (a) disulfide bonding of radioactive GP140 and fibronectin into the exogenous biotinylated matrix required cell contact with the matrix. The newly deposited GP140 and fibronectin derived from the cells and not from GP140 and fibronectin present in the conditioned culture media. (b) Pro-alpha 1 and Pro-alpha 2 procollagens, present in the culture media, bound to the exogenous matrix in a noncovalent manner and were independent of cell contact. (c) SV40 transformed cells (WI-38 VA13) synthesized released form GP140 but did not deposit GP140 into the biotinylated matrix.

scholarly journals Activation of the cell wall degrading protease, lysin, during sexual signalling in Chlamydomonas: the enzyme is stored as an inactive, higher relative molecular mass precursor in the periplasm.

1989 ◽  
Vol 108 (1) ◽  
pp. 199-207 ◽  
Author(s):  
M J Buchanan ◽  
S H Imam ◽  
W A Eskue ◽  
W J Snell
Keyword(s):  
Cell Wall ◽  
Molecular Mass ◽  
Mating Type ◽  
Gradient Centrifugation ◽  
Cell Contact ◽  
Relative Molecular Mass ◽  
Adhesive Interaction ◽  
Sds Page ◽  
Sexual Signalling ◽  
A Cell

During the mating reaction in Chlamydomonas reinhardtii mating type plus and mating type minus gametes adhere to each other via adhesion molecules on their flagellar surfaces. This adhesive interaction induces a sexual signal leading to release of a cell wall degrading enzyme, lysin, that causes wall release and degradation. In this article, we describe the preparation of a polyclonal antibody against the 60,000-Mr lysin polypeptide excised from SDS-PAGE gels. After absorption of the IgG with cell walls to remove antibodies against a carbohydrate epitope common to several Chlamydomonas glycoproteins, the immune IgG reacted with the 60,000-Mr polypeptide, and a 47,000-Mr species that we show here was immunologically cross-reactive with the 60,000-Mr molecule. By use of several fractionation methods including ion exchange and molecular sieve chromatography, sucrose gradient centrifugation, and affinity chromatography, we showed that the 60,000-Mr antigen copurified with lysin activity, thereby demonstrating that the antibody was indeed directed against the enzyme. Immunoblot experiments on suspensions of nonmating and mating gametes showed that the 60,000-Mr antigen was missing in the nonmating gametes. Instead, they contained a 62,000-Mr antigen that was not present in suspensions of mating gametes that had undergone sexual signalling. Furthermore, nonmating gametes whose walls were removed with exogenously added lysin did not contain either form of the antigen. We also found that the 62,000-Mr form of the antigen, which could be released from gametes by freeze-thawing, did not have wall degrading activity. These results indicate that lysin in gametes is stored in the periplasm as a higher relative molecular mass, inactive precursor and also that sexual signalling induces conversion of this molecule to a lower relative molecular mass, active enzyme. This may be a novel example of processing of an extracellular protease induced by cell contact.

scholarly journals Reelin is a serine protease of the extracellular matrix.

2002 ◽  
Vol 277 (13) ◽  
pp. 11616
Author(s):  
Carlo C. Quattrocchi ◽  
Francesca Wannenes ◽  
Antonio M. Persico ◽  
Silvia Anna Ciafré ◽  
Gabriella D'Arcangelo ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Serine Protease

Cell-to-cell contact and extracellular matrix

1994 ◽  
Vol 6 (5) ◽  
pp. 645-647 ◽  
Author(s):  
Alan F. Horwitz ◽  
Jean Paul Thiery
Keyword(s):  
Extracellular Matrix ◽  
Cell Contact

Cell-to-cell contact and extracellular matrix

1999 ◽  
Vol 11 (5) ◽  
pp. 535-536
Author(s):  
Jonathon Pines ◽  
Luca Toldo ◽  
Frank Lafont
Keyword(s):  
Extracellular Matrix ◽  
Cell Contact

Web alert: Cell-to-cell contact and extracellular matrix

2001 ◽  
Vol 13 (5) ◽  
pp. 523-524 ◽  
Author(s):  
Jonathon Pines ◽  
Frank Lafont
Keyword(s):  
Extracellular Matrix ◽  
Cell Contact

Cell-to-cell contact and extracellular matrix

2007 ◽  
Vol 19 (5) ◽  
pp. 493-494
Author(s):  
Lawrence Shapiro ◽  
Barry Honig
Keyword(s):  
Extracellular Matrix ◽  
Cell Contact

An overview of the α4β1 integrin and the potential therapeutic role of its antagonists

2021 ◽  
Vol 28 ◽  
Author(s):  
Elenilze F. B. Ferreira ◽  
Luciane B. Silva ◽  
Josiane V. Cruz ◽  
Pedro H. F. Araújo ◽  
Njogu M. Kimani ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Monoclonal Antibody ◽  
Extracellular Matrix ◽  
Inflammatory Responses ◽  
Cellular Responses ◽  
Tumour Invasion ◽  
Potential Therapeutic Role ◽  
Integrin Antagonists ◽  
Inside Out

: This article presents a simplified view of integrins with emphasis on the α4 (α4β1/VLA-4) integrin. Integrins are heterodimeric proteins expressed on the cell surface of leukocytes that participate in a wide variety of functions, such as survival, growth, differentiation, migration, inflammatory responses, tumour invasion, among others. When the extracellular matrix is degraded or deformed, cells are forced to undergo responsive changes that influence remodelling during physiological and pathological events. Integrins recognize these changes and trigger a series of cellular responses, forming a physical connection between the interior and the outside of the cell. The communication of integrins through the plasma membrane occurs in both directions, from the extracellular to the intracellular (outside-in) and from the intracellular to the extracellular (inside-out). Integrins are valid targets for antibodies and small molecule antagonists. One example is the monoclonal antibody natalizumab, marketed under the name of TYSABRI®, used in the treatment of recurrent multiple sclerosis, which inhibits the adhesion of α4 integrin to its counter-receptor. α4β1 Integrin antagonists are summarized here and their utility as therapeutics discussed.

Web alert Cell-to-cell contact and extracellular matrix

1997 ◽  
Vol 9 (5) ◽  
pp. 603-604
Author(s):  
Jonathon Pines ◽  
Luca Toldo ◽  
Frank Lafont
Keyword(s):  
Extracellular Matrix ◽  
Cell Contact

The localized assembly of extracellular matrix integrin ligands requires cell-cell contact

2000 ◽  
Vol 113 (21) ◽  
pp. 3715-3723 ◽  
Author(s):  
M.D. Martin-Bermudo ◽  
N.H. Brown
Keyword(s):  
Extracellular Matrix ◽  
Drosophila Embryo ◽  
Cell Contact ◽  
Primary Role ◽  
Dependent Manner ◽  
Muscle Attachment ◽  
Matrix Assembly ◽  
Attachment Sites ◽  
Genetically Manipulated ◽  
Cell Cell

The assembly of an organism requires the interaction between different layers of cells, in many cases via an extracellular matrix. In the developing Drosophila larva, muscles attach in an integrin-dependent manner to the epidermis, via a specialized extracellular matrix called tendon matrix. Tiggrin, a tendon matrix integrin ligand, is primarily synthesized by cells distant to the muscle attachment sites, yet it accumulates specifically at these sites. Previous work has shown that the PS integrins are not required for tiggrin localization, suggesting that there is redundancy among tiggrin receptors. We have examined this by testing whether the PS2 integrin can recruit tiggrin to ectopic locations within the Drosophila embryo. We found that neither the wild type nor modified forms of the PS2 integrin, which have higher affinity for tiggrin, can recruit tiggrin to new cellular contexts. Next, we genetically manipulated the fate of the muscles and the epidermal muscle attachment cells, which demonstrated that muscles have the primary role in recruiting tiggrin to the tendon matrix and that cell-cell contact is necessary for this recruitment. Thus we propose that the inherent polarity of the muscle cells leads to a molecular specialization of their ends, and interactions between the ends produces an integrin-independent tiggrin receptor. Thus, interaction between cells generates an extracellular environment capable of nucleating extracellular matrix assembly.

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