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Dive into the research topics where M. Saeed Khan is active.

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Featured researches published by M. Saeed Khan.


Biochemical and Biophysical Research Communications | 1985

Testosterone-estradiol-binding globulin binds to human prostatic cell membranes

Daniel J. Hryb; M. Saeed Khan; William Rosner

Specific binding sites for human testosterone-estradiol-binding globulin have been found on human prostatic cell membranes. Scatchard analysis reveals both a high and a low affinity binding site for [125I]testosterone-estradiol-binding globulin. The high affinity site is specific for testosterone-estradiol-binding globulin, whereas the low affinity site also binds human corticosteroid-binding globulin and human transferrin.


The Journal of Steroid Biochemistry and Molecular Biology | 1991

Sex hormone-binding globulin: Anatomy and physiology of a new regulatory system

William Rosner; Daniel J. Hryb; M. Saeed Khan; Atif M. Nakhla; Nicholas A. Romas

Sex hormone-binding globulin (SHBG) is a plasma glycoprotein that binds a number of circulating steroid hormones (testosterone, dihydrotestosterone and estradiol) with high affinity, thus regulating their free concentration in plasma. In addition to binding steroids, SHBG itself binds to receptor sites on plasma membranes with somewhat unusual kinetics. Both the off and on rates are quite slow. The steroid-binding and membrane-binding functions are intertwined in what is clearly an allosteric relationship. Occupation of SHBGs steroid-binding site by a steroid inhibits its ability to bind to its membrane receptor-binding site. This inhibition is not related to a steroids biological activity. Metabolites of steroids without biological activity, e.g. 2-methoxyestradiol, actively inhibit SHBGs interaction with its membrane receptor. However, if unliganded SHBG is allowed to bind to its receptor on intact cells, and an appropriate steroid hormone then is introduced, adenylate cyclase is activated and intracellular cAMP increases. This function is specific for steroids with biological activity, 2-methoxyestradiol has no activity in this arena. These observations demonstrate a potentially important role for SHBG as a regulator of cell function. They also demonstrate an additional mode of action of steroid hormones, one that does not require that the steroid interact with a steroid receptor.


Annals of the New York Academy of Sciences | 1988

Are corticosteroid - binding globulin and sex hormone - binding globulin hormones?

William Rosner; Daniel J. Hryb; M. Saeed Khan; Carol J. Singer; Atif M. Nakhla

Because it no longer seemed reasonable to us that the sole function of the steroid-binding proteins in plasma was to serve as a buffer reservoir for steroid hormones, we conducted experiments which sought out other possibilities. Both CBG and SHBG bind to cell membranes, and this interaction partakes of the general characteristics of peptide hormone-membrane receptor systems. Additionally, human CBG has the ability to cause an increase in the activity of membrane-bound adenylate cyclase in MCF-7 cells, and this, in turn, results in an increase in cellular cAMP content. Thus, CBG appears to be a protein hormone. As a first consideration, one might presume that because CBGs half-life is measured in days, it would be counted among the hormones which, for the most part, are tonic in their effects, e.g., thyroid hormone. However, two important considerations tend to believe this presumption: (1) CBG which is unoccupied by steroid is not hormonally active (Figure 5): (2) Depending upon the time of day, circulating CBG is approximately 0-60% occupied in normal humans. These observations result in a circumstance in which a substantial portion of circulating CBG is available for activation by bursts of cortisol secretion. It seems prudent to speculate that, because steroids are essential for CBGs activity, the hormonal role of CBG may be entwined with, or complementary to the steroids which it binds. Finally, we should comment on the impact that our model of CBG as a hormone has on the view that only unbound steroid can be hormonally active. First, it should be stated that we have not addressed this question experimentally. Although there is evidence that CBG may be required for cortisol action, we feel that an obligate role for it is not documented adequately. At this time, we believe that CBGs hormonal role is compatible with a hypothesis that encompasses the view that unbound steroid hormones can diffuse into cells in some tissues and that both free and bound steroid can enter cells in others. Obviously, the final word on these important topics, as always, awaits the proper experiments.


Steroids | 1985

Size isomers of testosterone-estradiol-binding globulin exist in the plasma of individual men and women

M. Saeed Khan; Paul H. Ehrlich; Steve Birken; William Rosner

We isolated testosterone-estradiol-binding globulin TeBG rapidly and in high yield from pooled pregnancy plasma. It showed two bands on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE). Both bands stained with three different monoclonal antibodies to TeBG, thus demonstrating their immunological similarity. Freshly drawn, individual sera, from men, women, and pregnant patients were submitted to microaffinity chromatography, a procedure which partially purifies TeBG in approximately 4 hr. The partially purified plasma was submitted to SDS PAGE, followed by immunoblotting. The blotted TeBG exhibited the same two bands seen in the isolated, purified protein. The size heterogeneity observed in TeBG purified to: proteolysis occurring during isolation; a peculiarity of pregnancy plasma; or heterogeneity attendant upon the use of pooled plasma for isolation.


The Journal of Clinical Endocrinology and Metabolism | 1984

HORMONAL INFLUENCES ON THE SECRETION OF STEROID-BINDING PROTEINS BY A HUMAN HEPATOMA-DERIVED CELL LINE

William Rosner; David P. Aden; M. Saeed Khan


The Journal of Clinical Endocrinology and Metabolism | 1981

SECRETION OF TESTOSTERONE-ESTRADIOL-BINDING GLOBULIN BY A HUMAN HEPATOMA-DERIVED CELL LINE

M. Saeed Khan; Barbara B. Knowles; David P. Aden; Rosne Rosne


The Journal of Clinical Endocrinology and Metabolism | 1982

Radioimmunoassay for Human Testosterone-Estradiol Binding Globulin*

M. Saeed Khan; Elsie C. Ewen; William Rosner


Journal of Andrology | 1992

Sex Hormone-Binding Globulin Binding to Cell Membranes and Generation of a Second Messenger

William Rosner; Daniel J. Hryb; M. Saeed Khan; Atif M. Nakhla; Nicholas A. Romas


Journal of Steroid Biochemistry | 1984

Human corticosteroid binding globulin is secreted by a hepatoma-derived cell line

M. Saeed Khan; David P. Aden; William Rosner


The Journal of Clinical Endocrinology and Metabolism | 1976

Identification of Corticosteroid-Binding Globulin in Human Milk: Measurement with a Filter Disk Assay

William Rosner; Philip C. Beers; Tayyiba Aw An; M. Saeed Khan

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Marjorie Safran

University of Massachusetts Medical School

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