Metabolic regulation of steroidogenesis in adrenocortical carcinoma cells of rat. Effect of adrenocorticotropin and adenosine cyclic 3',5'-monophosphate on the incorporation of (20S)-20-hydroxy(7 alpha-3H)cholesterol into deoxycorticosterone and corticosterone

Multilimbed membrane guanylate cyclase signaling system, evolutionary ladder

One monumental discovery in the field of cell biology is the establishment of the membrane guanylate cyclase signal transduction system. Decoding its fundamental, molecular, biochemical, and genetic features revolutionized the processes of developing therapies for diseases of endocrinology, cardio-vasculature, and sensory neurons; lastly, it has started to leave its imprints with the atmospheric carbon dioxide. The membrane guanylate cyclase does so via its multi-limbed structure. The inter-netted limbs throughout the central, sympathetic, and parasympathetic systems perform these functions. They generate their common second messenger, cyclic GMP to affect the physiology. This review describes an historical account of their sequential evolutionary development, their structural components and their mechanisms of interaction. The foundational principles were laid down by the discovery of its first limb, the ACTH modulated signaling pathway (the companion monograph). It challenged two general existing dogmas at the time. First, there was the question of the existence of a membrane guanylate cyclase independent from a soluble form that was heme-regulated. Second, the sole known cyclic AMP three-component-transduction system was modulated by GTP-binding proteins, so there was the question of whether a one-component transduction system could exclusively modulate cyclic GMP in response to the polypeptide hormone, ACTH. The present review moves past the first question and narrates the evolution and complexity of the cyclic GMP signaling pathway. Besides ACTH, there are at least five additional limbs. Each embodies a unique modular design to perform a specific physiological function; exemplified by ATP binding and phosphorylation, Ca²⁺-sensor proteins that either increase or decrease cyclic GMP synthesis, co-expression of antithetical Ca²⁺ sensors, GCAP1 and S100B, and modulation by atmospheric carbon dioxide and temperature. The complexity provided by these various manners of operation enables membrane guanylate cyclase to conduct diverse functions, exemplified by the control over cardiovasculature, sensory neurons and, endocrine systems.

ACTH-Modulated Membrane Guanylate Cyclase Signaling System: Origin and Creation

The membrane guanylate cyclase (MGC) cellular signaling pathway consists of seven signaling pathways and is critical for the survival of prokaryotes eukaryotes, and highly complex vertebrate organisms. A sequel to the author's earlier comprehensive reviews, covering the field of MGC from its origin to its establishment to the year 2014, this article exclusively deals with the history of its development from the year 1963 to 1987. It narrates the efforts involved in building on small projects, brick by brick, and its emergence from the chasm of disbelief, through steady, continuous work. To make the presentation simple and chronologically continuous, the subject matters of the earlier reviews and publication of these authors have been freely borrowed with appropriate citations.

Biosynthesis and metabolism of steroid hormones by human adrenal carcinomas

Over a 15-year period, our university-based laboratory obtained 125 adrenal tumors, of which 15 (12%) were adrenal cortical carcinomas. Of these, 6 (40% of the carcinomas) occurred in patients with clear clinical manifestations of steroid hormone excess. Adrenal cortical carcinoma cells derived from the surgically resected tumors in 4 of these patients were isolated and established in primary culture. Radiotracer steroid interconversion studies were carried out with these cultures and also on mitochondria isolated from homogenized tissues. Large tumors had the lowest steroidogenic activities per weight, whereas small tumors had more moderately depressed enzyme activities relative to cells from normal glands. In incubations with pregnenolone as substrate, 1 mM metyrapone blocked the synthesis of corticosterone and cortisol and also the formation of aldosterone. Metyrapone inhibition was associated with a concomitant increase in the formation of androgens (androstenedione and testosterone) from pregnenolone. Administration of metyrapone in vivo before surgery in one patient resulted in a similar increase in plasma androstenedione, though plasma testosterone levels were not significantly affected. In cultures of two of four tumors examined, dibutyryl cAMP stimulated 11ss-hydroxylase activity modestly; ACTH also had a significant stimulatory effect in one of these tumors. Unlike results obtained with normal or adenomatous adrenal cortical tissues, mitochondria from carcinomatous cells showed a lack of support of either cholesterol side-chain cleavage enzyme complex or steroid 11ss-hydroxylase activity by Krebs cycle intermediates (10 mM isocitrate, succinate or malate). This finding is consistent with the concept that these carcinomas may tend to function predominantly in an anaerobic manner, rather than through the oxidation of Krebs cycle intermediates.

Cholesterol autoxidation 1981-1986

Literature published between 1980 and 1986 dealing broadly with the topic of cholesterol autoxidation is reviewed. The review builds on the detailed 1981 monographic treatment of the topic by the author and covers new items of chemistry, analysis, and metabolism.

Adenosine 3',5'-monophosphate-dependent protein kinase from normal human adrenal

The protein kinase of normal human adrenal cytosol has been resolved by DEAE-cellulose chromatography into two major components, the protein kinases I and II, which are both adenosine 3',5'-monophosphate (cAMP) dependent. Both enzymes have similar substrate specificities, cAMP-dependency, and sensitivity to the stimulation by this nucleotide, but differ in their states of activation after preincubation with histone. The DEAE--cellulose charomatography of dissociated cytosol protein kinase reveals only one peak of kinase activity and two peaks of cAMP binding activity (A and B). Both binding proteins are able to inhibit the kinase activity of the catalytic subunit. Recombination experiments suggest that the regulatory subunit A originated from protein kinase I and subunit B from protein kinase II. The phosphorylation of histone by adrenal protein kinases is inhibited by a heat-stable protein inhibitor isolated from human fetal brain and human adult adrenal.