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(Circulation Research. 2006;99:790.)
© 2006 American Heart Association, Inc.

Editorials

A Single Second Messenger

Several Possible Cellular Responses Depending on Distinct Subcellular Pools

Karin E. Bornfeldt

From the Department of Pathology, University of Washington, Seattle.

Correspondence to Karin E. Bornfeldt, Department of Pathology, Box 357470, University of Washington School of Medicine, Seattle, WA 98195-7470. E-mail bornf@u.washington.edu

See related article, pages 845–852

Key Words: adenylyl cyclase • editorial • proliferation • second messengers • smooth muscle cell

An extract of the first 250 words of the full text is provided, because this article has no abstract.

	Multiple Enzyme Isoforms Provide the Cell With Tools to Precisely Control Second Messenger Levels

 
Second messengers are defined as small molecules that are synthesized in the cell in response to extracellular first messengers,¹ and diffuse through the cytoplasm to mediate their effects. This definition is sometimes broadened to include hydrophobic molecules, such as diacylglycerol (DAG).² Synthesis and degradation of second messengers are regulated by a number of enzymes expressed in mammalian cells. Such enzymes include, but are not limited to, adenylyl cyclase (AC) for synthesis of cyclic AMP (cAMP), guanylyl cyclase for synthesis of cyclic GMP (cGMP), cyclic nucleotide phosphodiesterase (PDE) for hydrolysis of cAMP and cGMP, and phospholipase C (PLC) for hydrolysis of phosphatidylinositol 4,5-bisphosphate to inositol 1,4,5-trisphosphate (IP₃) and DAG. Each of these enzyme groups consists of a plethora of isoforms. Thus, there are 10 different gene products in the mammalian AC gene family (AC1–9 and an atypical soluble AC isoform).^3–5 Furthermore, different splice variants of AC4, AC5, and AC8 have been cloned.^6–8 A large number of PDE and PLC isoforms have also been cloned. To date, 21 different PDE genes divided among 11 gene families have been identified in mammals.⁹ Most PDE families consist of more than 1 gene products, and most genes code for more than 1 messenger RNA. Although some PDE gene families hydrolyze cAMP exclusively (PDE4, PDE7, and PDE8), many of these enzymes hydrolyze both cAMP and cGMP (PDE1, PDE2, PDE3, PDE10, and PDE11), and some hydrolyze cGMP exclusively (PDE5, PDE6, and PDE9).⁹ There are at least 13 different PLC isoforms generating IP₃ and DAG, which also . . . [Full Text of this Article]

Related Article:

Adenylyl Cyclase Isoform–Selective Regulation of Vascular Smooth Muscle Proliferation and Cytoskeletal Reorganization

Robert Gros, Qingming Ding, Jozef Chorazyczewski, J. Geoffrey Pickering, Lee E. Limbird, and Ross D. Feldman
Circ. Res. 2006 99: 845-852. [Abstract] [Full Text] [PDF]

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