Steroidogenic cells lipid droplets

The StAR protein was first identified, characterized and named by Dr. Douglas Stocco at Texas Tech University Health Sciences Center in 1994. [18] The role of this protein in lipoid CAH was confirmed the following year in collaboration with Dr. Walter Miller at the University of California, San Francisco . [19] All of this work follows the initial observations of the appearance of this protein and its phosphorylated form coincident with factors that caused steroid production by Dr. Nanette Orme-Johnson while at Tufts University . [20]

Recently, a specific peptide inhibitor for ATGL was isolated from white blood cells, specifically mononuclear cells. This peptide was originally identifed as being involved in the regulation of the G 0 to G 1 transition of the cell cycle . This peptide was, therefore, called G0G1 switch protein 2 (G0S2). The protein is found in numerous tissues, with highest concentrations in adipose tissue and liver. In adipose tissue G0S2 expression is very low during fasting but increases after feeding. Conversely, fasting or PPARα-agonists increase hepatic G0S2 expression. The protein has been shown to localize to LDs, cytoplasm, ER, and mitochondria. These different subcellular localizations likely relate to multiple functions for G0S2 in regulating lipolysis, the cell cycle , and, possibly, apoptosis via its ability to interact with the mitochondrial antiapoptotic factor Bcl-2. With respect to ATGL regulation, the binding of the enzyme to LDs and subsequent is dependent on a physical interaction between the N-terminal region of G0S2 and the patatin domain of ATGL.

However, there are several other lesser-known mechanisms of generating NADPH, all of which depend on the presence of mitochondria. The key enzymes in these processes are: NADP-linked malic enzyme , NADP-linked isocitrate dehydrogenase , NADP-linked glutamate dehydrogenase and nicotinamide nucleotide transhydrogenase. [1] The isocitrate dehydrogenase mechanism appears to be the major source of NADPH in fat and possibly also liver cells. [2] Also, in mitochondria, NADH kinase produces NADPH and ADP, using NADH and ATP as substrates.

LD-associated proteins can be cytosol-derived proteins or ER-derived proteins [ 26 ]. Their regulation is finely controlled and responds to physiological conditions, like fasting and feeding and hormones. Further, their expression varies depending on cell and tissue types. Different PLIN combinations on the LD surface would confer LD tissue specificity [ 27 , 28 ]. Interestingly, Hsieh et al. showed that LD composition and localization can vary at a single cell level. In particular, FA-enriched LDs localize preferentially to the cell periphery, while CE-enriched LDs to central regions. Besides, in various cell types, different exogenous lipid stimuli exert differential effects on perilipin coating and differential targeting of perilipins to different classes of LDs [ 29 ].

Steroidogenic cells lipid droplets

steroidogenic cells lipid droplets

LD-associated proteins can be cytosol-derived proteins or ER-derived proteins [ 26 ]. Their regulation is finely controlled and responds to physiological conditions, like fasting and feeding and hormones. Further, their expression varies depending on cell and tissue types. Different PLIN combinations on the LD surface would confer LD tissue specificity [ 27 , 28 ]. Interestingly, Hsieh et al. showed that LD composition and localization can vary at a single cell level. In particular, FA-enriched LDs localize preferentially to the cell periphery, while CE-enriched LDs to central regions. Besides, in various cell types, different exogenous lipid stimuli exert differential effects on perilipin coating and differential targeting of perilipins to different classes of LDs [ 29 ].

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