Article

Nonhepathic origin of notothenioid antifreeze reveals pancreatic synthesis as common mechanism in polar fish freezing avoidance. Proc Natl Acad Sci USA

Department of Animal Biology, University of Illinois, Urbana, IL 61801, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 08/2006; 103(27):10491-6. DOI: 10.1073/pnas.0603796103
Source: PubMed

ABSTRACT

Phylogenetically diverse polar and subpolar marine teleost fishes have evolved antifreeze proteins (AFPs) or antifreeze glycoproteins (AFGPs) to avoid inoculative freezing by internalized ice. For over three decades since the first fish antifreeze (AF) protein was discovered, many studies of teleost freezing avoidance showed hepatic AF synthesis and distribution within the circulation as pivotal in preventing the blood, and therefore the fish, from freezing. We have uncovered an important twist to this long-held paradigm: the complete absence of liver synthesis of AFGPs in any life stage of the Antarctic notothenioids, indicating that the liver plays no role in the freezing avoidance in these fishes. Instead, we found the exocrine pancreas to be the major site of AFGP synthesis and secretion in all life stages, and that pancreatic AFGPs enter the intestinal lumen via the pancreatic duct to prevent ingested ice from nucleating the hyposmotic intestinal fluids. AFGPs appear to remain undegraded in the intestinal milieu, and the composition and relative abundance of intestinal AFGP isoforms are nearly identical to serum AFGPs. Thus, the reabsorption of intact pancreas-derived intestinal AFGPs, and not the liver, is the likely source of circulatory AFGPs in notothenioid fishes. We examined diverse northern fish taxa and Antarctic eelpouts with hepatic synthesis of bloodborne AF and found that they also express secreted pancreatic AF of their respective types. The evolutionary convergence of this functional physiology underscores the hitherto largely unrecognized importance of intestinal freezing prevention in polar teleost freezing avoidance, especially in the chronically icy Antarctic waters.

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    • "Убедительно говорят об этом примеры гетеротопного параллелизма как на видовом (фии логенетическом) уровне организации (независии мое сходство молекул у тресковых в Арктике и ноо тотениевидных в Антарктике и, возможно, в разз ных филогенетических ветвях Notothenioidei (Chen et al., 1997; Matschiner et al., 2011)), так и на организменном (онтогенетическом) уровне (синн тез молекул у тресковых и в желудочноокишечч ном тракте, и в печени). Хотя в последнем аспекте нототениевидные рыбы кажутся исключением, поскольку у них синтез гликопротеинов в печени не подтверждён (Cheng et al., 2006), но обнаружее ние гликопротеинов в их кожной слизи свидее тельствует о наличии у этих рыб гетеротопного синтеза AFGP. В геноме нототениевидных могут быть разные копии генов AFGP, подобно тому, что, например, имеет место с генами AFP типа I у американской, или зимней, камбалы Pseudopleuu ronectes americanus. "
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    • "The impacts of low temperatures and seasonally limited food availability have long been recognized as primary selective forces driving the evolution of the many endemic species found in Antarctica today [4-8]. In addition to the high degree of endemism produced by these evolutionary processes, a wide-array of functional adaptations have been fixed among protein families of several Antarctic fish, including chaperonins [9], heat shock proteins [10,11], heme proteins [12,13], tubulin kinetics [14], and anti-freeze proteins [15,16]. This rigid oceanographic stability however, may have resulted in an ecosystem filled with endemic fauna that are poorly poised to deal with rapid climate variation [7,17]. "
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    • "Убедительно говорят об этом примеры гетеротопного параллелизма как на видовом (фии логенетическом) уровне организации (независии мое сходство молекул у тресковых в Арктике и ноо тотениевидных в Антарктике и, возможно, в разз ных филогенетических ветвях Notothenioidei (Chen et al., 1997; Matschiner et al., 2011)), так и на организменном (онтогенетическом) уровне (синн тез молекул у тресковых и в желудочноокишечч ном тракте, и в печени). Хотя в последнем аспекте нототениевидные рыбы кажутся исключением, поскольку у них синтез гликопротеинов в печени не подтверждён (Cheng et al., 2006), но обнаружее ние гликопротеинов в их кожной слизи свидее тельствует о наличии у этих рыб гетеротопного синтеза AFGP. В геноме нототениевидных могут быть разные копии генов AFGP, подобно тому, что, например, имеет место с генами AFP типа I у американской, или зимней, камбалы Pseudopleuu ronectes americanus. "
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