Generation, characterization and ELISA of monospecific antibodies against the subunits of a Ca2+-dependent protein kinase and a Ca2+-transport ATPase from rabbit skeletal muscle

Ubiquitin and the enigma of intracellular protein degradation

Contrary to widespread belief, the regulation and mechanism of degradation for the mass of intracellular proteins (i.e. differential, selective protein turnover) in vertebrate tissues is still a major biological enigma. There is no evidence for the conclusion that ubiquitin plays any role in these processes. The primary function of the ubiquitin-dependent protein degradation pathway appears to lie in the removal of abnormal, misfolded, denatured or foreign proteins in some eukaryotic cells. ATP/ubiquitin-dependent proteolysis probably also plays a role in the degradation of some so-called 'short-lived' proteins. Evidence obtained from the covalent modification of such natural substrates as calmodulin, histones (H2A, H2B) and some cell membrane receptors with ubiquitin indicates that the reversible interconversion of proteins with ubiquitin followed by concomitant functional changes may be of prime importance.

Role of laminin autoantibodies on the embryo toxicity of sera from mercuric chloride treated brown Norway rats

In previous studies, antilaminin antibodies were found to be toxic to cultured rat embryos. In order to extend these studies, Brown Norway rats were treated with mercuric chloride, which led to the production of laminin autoantibodies. Sera samples from brown Norway rats treated with mercuric chloride were found to be teratogenic as well as lethal to cultured rat embryos. This embryotoxicity was not associated with sera mercury levels, but was related to the levels of antilaminin antibodies in sera. Affinity purified laminin antibodies from these mercuric chloride treated Brown Norway rats, when added to control sera, were found to be teratogenic but not lethal. These antibodies were found to bind to the laminin sequences IKVAV (A chain) and YIGSR (B1 chain), but not RGD (A chain) or YD (B1 chain). These observations suggested the possibility that an environmental pollutant such as mercury could cause the formation of embryotoxic autoantibodies that could persist in the body as embryotoxic factors for extended periods of time.

Toxicity of sera from individuals with Chagas' disease to cultured rat embryos: role of antibodies to laminin

In previous studies antilaminin antibodies in the sera of immunized monkeys and rats were found to be toxic to cultured rat embryos. In order to extend these studies to humans, head-fold stage rat embryos were cultured for 48 hours on ten different serum samples from individuals with Chagas' disease. All embryos (n = 20) cultured on these sera were found to be abnormal. Using ELISA, Western immunoblot, and indirect immunofluorescence it could be shown that antibodies in these sera reacted with laminin. That these antilaminin antibodies were, at least in part, responsible for the toxicity was indicated 1) by reduced cultured embryo toxicity for six of seven serum samples after pre-absorption with purified laminin, 2) by demonstrating a relationship between the amount of affinity-purified antilaminin IgG added to control serum for culture and the severity of embryo abnormalities seen at the end of culture, and 3) by the sera's failing to react with other basement membrane proteins, including type IV collagen, fibronectin, osteonectin, and heparan sulfate proteoglycan.

Laminin immunized monkeys develop sera toxic to cultured rat embryos and fail to reproduce

In a previous study antilaminin antibodies in a monkey with a poor reproductive history were found to be the cause of serum toxicity to cultured rat embryos. In the present study four monkeys were immunized with murine tumor laminin and a fifth with bovine serum albumin. Subsequently, sera from only the laminin immunized monkeys became toxic to cultured rat embryos. This serum toxicity was not mediated by complement but did require the antibody to have a divalent structure. Finally, mating trials were conducted with two of the laminin immunized monkeys that previously had excellent reproductive histories. Based on progesterone levels and observation the monkeys continued to have normal menstrual cycles but failed to initiate a successful pregnancy following immunization in over 2 years of mating trials. These data demonstrated that antibodies against laminin could have prevented conception or could have interrupted pregnancy because of embryotoxicity or failure of implantation.

In vitro and in vivo embryo toxicity of antilaminin antibodies in the rat

Rats mated after laminin immunization had higher frequencies of resorptions (57%) than those immunized with bovine serum albumin (20%) and had sera that were toxic to cultured rat embryos. In addition, sera from rats immunized with laminin A chains but not B chains were toxic to cultured embryos. The toxicity of sera to embryos was related to the reactivity of sera to specific laminin fragments rather than to sera IgG levels against intact laminin. In addition, resorptions in pregnant rats immunized with laminin were not related to the sera antilaminin IgG levels. However, levels of uterine antilaminin IgA, the predominant uterine isotype, increased considerably during the first 3.5 days of pregnancy, while sera antilaminin IgG remained constant. (Am J Reprod Immunol.

Activation and inhibition of phosphorylase kinase by monospecific antibodies against preparatively isolated alpha, beta and gamma subunits

Homogeneous alpha and beta subunits were isolated for the first time in preparative amounts in the presence of sodium dodecyl sulfate. Analysis by analytical polyacrylamide electrophoresis, sedimentation velocity, and immunoprecipitation with monospecific antibodies indicated homogeneity. The apparent molecular masses of the purified subunits as determined electrophoretically in the presence of dodecyl sulfate are: alpha = 140.2 +/- 2.1 kDa and beta = 123 +/- 1.8 kDa. Amino acid analyses show that per 100 mol amino acid the alpha-subunit has a higher serine content (Ser alpha/Ser beta = 1.32, Ser alpha/Ser gamma = 1.42) and a lower aspartic acid/asparagine (Asx) content (AsX alpha/Asx beta = 0.76, Asx alpha/Asx gamma = 0.90) than the beta and gamma subunits. Monospecific antibodies against the purified alpha, beta and gamma subunits were produced in sheep [J. Immunol. Methods (1984) 70, 193-209] and their action on the catalytic activity of non-activated phosphorylase kinase assayed. It can be shown that certain antibody fractions of anti-alpha, anti-beta and anti-gamma inhibit the Ca2+-dependent and Ca2+-independent activity at pH 6.8 as well as at pH 8.2. Other antibody fractions against the beta and gamma subunits however activate the Ca2+-dependent activity at pH 6.8 threefold to fourfold, although they inhibit the activity at pH 8.2. These antibodies lead to a ca. five fold increase in the pH 6.8/8.2 activity ratio. Activating anti-beta can even overcome the inhibitory action of anti-alpha at pH 6.8. A kinetic analysis shows that inhibition is the result of a mixed type mechanism whereas activation is due to a fivefold to tenfold increase in V for phosphorylase b. The results illustrate the importance of possibly large, concerted conformational changes of phosphorylase kinase. It appears that activation or inhibition can be triggered by the antibody binding to conformational determinants of a single subunit type leading to a structural alteration of the holoenzyme.