Mechanisms, Detection, and Relevance of Protein Acetylation in Prokaryotes.

Posttranslational modification of a protein, either alone or in combination with other modifications, can control properties of that protein, such as enzymatic activity, localization, stability, or interactions with other molecules. N-ε-Lysine acetylation is one such modification that has gained attention in recent years, with a prevalence and significance that rival those of phosphorylation. This review will discuss the current state of the field in bacteria and some of the work in archaea, focusing on both mechanisms of N-ε-lysine acetylation and methods to identify, quantify, and characterize specific acetyllysines. Bacterial N-ε-lysine acetylation depends on both enzymatic and nonenzymatic mechanisms of acetylation, and recent work has shed light into the regulation of both mechanisms. Technological advances in mass spectrometry have allowed researchers to gain insight with greater biological context by both (i) analyzing samples either with stable isotope labeling workflows or using label-free protocols and (ii) determining the true extent of acetylation on a protein population through stoichiometry measurements. Identification of acetylated lysines through these methods has led to studies that probe the biological significance of acetylation. General and diverse approaches used to determine the effect of acetylation on a specific lysine will be covered.

Glibenclamide improves postischemic recovery of myocardial contractile function in trained and sedentary rats.

In this study, we sought to determine whether there was any evidence for the idea that cardiac ATP-sensitive K+ (K(ATP)) channels play a role in the training-induced increase in the resistance of the heart to ischemia-reperfusion (I/R) injury. To do so, the effects of training and an K(ATP) channel blocker, glibenclamide (Glib), on the recovery of left ventricular (LV) contractile function after 45 min of ischemia and 45 min of reperfusion were examined. Female Sprague-Dawley rats were sedentary (Sed; n = 18) or were trained (Tr; n = 17) for >20 wk by treadmill running, and the hearts from these animals used in a Langendorff-perfused isovolumic LV preparation to assess contractile function. A significant increase in the amount of 72-kDa class of heat shock protein was observed in hearts isolated from Tr rats. The I/R protocol elicited significant and substantial decrements in LV developed pressure (LVDP), minimum pressure (MP), rate of pressure development, and rate of pressure decline and elevations in myocardial Ca(2+) content in both Sed and Tr hearts. In addition, I/R elicited a significant increase in LV diastolic stiffness in Sed, but not Tr, hearts. When administered in the perfusate, Glib (1 microM) elicited a normalization of all indexes of LV contractile function and reductions in myocardial Ca(2+) content in both Sed and Tr hearts. Training increased the functional sensitivity of the heart to Glib because LVDP and MP values normalized more quickly with Glib treatment in the Tr than the Sed group. The increased sensitivity of Tr hearts to Glib is a novel finding that may implicate a role for cardiac K(ATP) channels in the training-induced protection of the heart from I/R injury.

Endurance training alters outward K+ current characteristics in rat cardiocytes.

The effect of endurance run training on outward K+ currents with rapidly inactivating (I(to)) and sustained or slowly inactivating (I(sus)) characteristics was examined in left ventricular (LV) cardiocytes isolated from sedentary (Sed) and treadmill-trained (Tr) female Sprague-Dawley rats. Isolated LV cardiocytes were used in whole cell patch-clamp studies to characterize whole cell I(to) and I(sus). Peak I(to) was greatest in cells isolated from the Tr group. When I(to) was corrected for cell capacitance to yield a current density, most, but not all, of the Sed vs. Tr differences in I(to) magnitude were eliminated. Regardless of how I(to) was expressed (e.g., I(to) or I(to) density), the time required to achieve a peak value was markedly shortened in the cardiocytes isolated from the Tr group. Training elicited a reduction in I(sus) density. Action potential characteristics were determined in Sed and Tr cardiocytes in primary culture. Training did not affect resting membrane potential, whereas peak membrane potential was reduced and time to peak membrane potential was prolonged in the Tr group. In addition, time to 50% repolarization was significantly increased in cells from the Tr group. Collectively, these data indicate that I(to) and I(sus) characteristics are altered by training in isolated LV cardiocytes. These alterations in I(to) and I(sus) may be responsible, at least in part, for the training-induced alterations in action potential configuration in cardiocytes in primary culture.

Phenylalanine hydroxylase expression in liver of a fetus with phenylketonuria.

The expression and activity of phenylalanine hydroxylase was studied in the liver of a fetus aborted after prenatal diagnosis of phenylketonuria. No phenylalanine hydroxylase enzymatic activity or immunoreactive protein was detectable in the PKU liver specimen, though both enzymatic activity and immunoreactive protein were detectable in control specimens of similar gestational age. Phenylalanine hydroxylase messenger RNA of normal size was present in the PKU fetal liver at normal abundance. These results confirm the genetic diagnosis of PKU in this fetus and indicate that the mutations in this fetus affect translation or stability of the phenylalanine hydroxylase protein.

Maternal phenylketonuria.

Pregnant women with untreated phenylketonuria (PKU) with blood phenylalanine levels greater than 1200 mumol/L usually give birth to offspring with congenital birth defects, including microcephaly, cardiac defects and mental retardation. According to Mabry and Levy, hyperphenylalaninaemic (HPA) women with blood phenylalanine levels between 600 and 1200 mumol/L also have an increased risk to their offspring. To study this problem further, the National Institute of Child Health and Human Development has established a collaborative study for 7 years to elucidate a proper treatment programme for these women.

Meningoencephalitis complicated by pituitary insufficiency and a spontaneously resolving suprasellar mass.

A 53-year-old woman presented with acute meningoencephalitis associated with anterior and posterior pituitary insufficiency. A computed axial tomogram (CT) of the head revealed a suprasellar mass. The meningoencephalitis, presumably of bacterial origin, resolved after antibiotic therapy and, on a repeat CT, the suprasellar mass had disappeared. Five months after the initial illness, the patient's diabetes insipidus had resolved, anterior pituitary function had improved, and there was no sign of the suprasellar mass. The presence of a suprasellar mass in conjunction with acute meningoencephalitis and anterior and posterior pituitary insufficiency should raise the suspicion that the mass is not neoplastic and may be infectious or inflammatory in origin.

Reproductive counselling for adolescent females with phenylketonuria.

It is our goal to provide young adolescents with the information needed to make an informed choice, and a support system for them and their families, in whatever they choose. 1. Sterilization is not advocated. 2. Pregnancy is not advocated. 3. Reliable birth control methods are encouraged. 4. Organized reproductive counseling is essential using concrete problem solving--diagram, taste tests, etc. 5. Diet trial before or during pregnancy requires an informed understanding of the responsibilities of parenthood.