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Protein aggregation as an element of aging
process
Protein aggregation is one of the common characteristics of
aging. It is a consequence of abnormalities of protein structure
induced by destructive actions (free radicals, mechanical impact,
temperature) but also by abnormalities of synthesis, mainly due
to mutation. The cell defends itself by destroying abnormally
structured proteins, determining short life span for unstable
proteins, altering the rate of synthesis and the rate of protein
elimination. Metabolism gradually slows down with aging and
the amount of abnormally structured proteins increases which
in consequence accelerates the rate of aggregation [34, 35].
A constellation of pathological processes that ensue are natural
companions of aging.
Discussion
The mechanism that determines red blood cell death is eryth-
rocyte speciic and underlies the universal character of dying
in nature. As a consequence, the deinition of life appears to
refer to automation that provides biological structures with the
features of life, but belonging to the living world is determined
by the programmed duration of functioning terminated by death.
A living thing is then a form of animated nature, which has
the features of independence as a result of automation and pos-
sesses its own compatible with nature program of action which
is time-limited beforehand.
In accordance with this deinition living things are those
natural creatures which form the integral part of nature promot-
ing its development. It means that Nature creates things deined
as living providing them with the features of independence and
simultaneously limiting their time of function. Only combined
conditions determine the consistency with animated nature and
provide a basis for interpreting the forms of nature as living. In
this sense immortal cells are not consistent with nature, and they
may be regarded as automatic structures similar to man-made
robots. In turn, viruses lacking independence may correspond
to cell destroying venoms and toxins.
Among the characteristics of living things one feature appears
universal and it is the presence of clock mechanisms. An oscilla
-
tor is a system that includes a negative feedback loop, which is
coupled with a positive feedback loop to obtain appropriate signal
characteristics [7, 36]. They usually involve a speciic process
serving as the basis of time but as a result of cooperation they
cover much wider range of functions.The universality of variable
frequency oscillators, which are encountered in almost all cells
(including bacterial cells), appears to emphasize the real need
for self-sustained rhythmic activity. The frequency of oscillations
ranges from one cycle per second to one cycle per day or even
per year. Humans have circadian rhythms coordinated by one
master clock being superior to peripheral oscillators. The circadian
rhythm in humans developed in line with the evolution of life on
Earth in the light-dark cycle. The role of the circadian rhythm
may be to anticipate changes in individual activity related to the
onset of daylight. For this reason the master clock in humans (the
suprachiasmatic nucleus - SCN) is linked to the retina through
neuronal communication [6].
Variable frequency oscillators in cells (regulation of glyco-
lytic enzyme activity, changes in the concentration of calcium
ions and others) perform a different function. They include
a regulatory feedback loop between DNA and protein. The
function of the master clock in humans is regulated by cyclic
changes in the activity of the transcription factors CLOCK and
BMAL-1 acting as transcriptional repressor (upon Per and
Cry proteins).
The role of this phenomenon is not clear yet. Evidence shows
that there is a relationship between the presence of oscillators and
various individual processes in the cell. However, the universality
of this phenomenon may imply its general and fundamental role
of maintaining an active form of life processes, which being auto-
matically controlled have a natural tendency toward minimizing
their activity upon reaching the programmed level.
Further studies are warranted to answer the question whether
the presence of oscillators is a characteristic feature and a pre-
requisite for life and whether it may be considered as one of
its criteria.
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System biolog
y
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