Changes in isoform composition, structure, and functional properties of titin from mongolian gerbil (Meriones unguiculatus) cardiac muscle after space flight

Abstract

Changes in isoform composition, secondary structure, and titin phosphorylation in Mongolian gerbil (Meriones unguiculatus) cardiac muscle were studied after 12-day-long space flight onboard the Russian spacecraft Foton-M3. The effect of titin on the actin-activated myosin ATPase activity at pCa 7.5 and 4.6 was also studied. Almost twofold increase in titin long N2BA isoform content relative to that of short N2B isoform was found on electrophoregrams of cardiac muscle left ventricle of the flight group gerbils. Differences in secondary structure of titin isolated from cardiac muscle of control and flight groups of gerbils were found. An increase in phosphorylation (1.30-1.35-fold) of titin of cardiac muscle of the flight group gerbils was found. A decrease in activating effect of titin of cardiac muscle of the flight group gerbils on actomyosin ATPase activity in vitro was also found. The observed changes are discussed in the context of M. unguiculatus cardiac muscle adaptation to conditions of weightlessness.

Nuances of electrophoresis study of titin/connectin

“…SDS gel electrophoresis was carried out according to Granzier and Irving (1995 no nucleic acids in the bands, although western blots with 9D10 antibodies revealed titin bands (Vikhlyantsev et al 2004a). Our subsequent studies showed that these titin bands appear in the electrophoregrams of striated muscles of humans and other mammals, including mouse, rat, rabbit (Vikhlyantsev and Podlubnaya 2006;Ulanova et al 2015), ground squirrel , Mongolian gerbil (Vikhlyantsev et al 2011;Okuneva et al 2012), and bear . Titin isoform composition in striated muscles in other groups of vertebrates (amphibians and birds) revealed no NT bands .…”

Seasonal changes in isoform composition of giant proteins of thick and thin filaments and titin (connectin) phosphorylation level in striated muscles of bears (Ursidae, Mammalia)

“…The purity of isolated titin preparations was tested by electrophoresis in macro porous polyacrylamide gel strengthened with agarose in the presence of SDS. Isolation of actin and myosin from rabbit muscles and investigation of the effect of titin on the actin activated ATPase activity of myosin in vitro were carried out as described previously [18].…”

“…The T2 fragment of titin inter acting with myosin filaments in the sarcomere also under goes phosphorylation. In vitro studies showed that T2, containing more PO 3 groups, activated the ATPase activ ity of actomyosin to a lesser extent [18,39]. In view of the data on the increase (~1.5 fold) in the phosphorylation level of T2 isolated from the skeletal muscles of ground squirrels in the state of torpidity, an inhibitory role of titin phosphorylation in the contractile activity of skeletal muscles of these animals during hibernation was suggest ed [39].…”

Structure of cortical cytoskeleton in fibers of mouse muscle cells after being exposed to a 30-day space flight on board the BION-M1 biosatellite

“…In addition, the state of other proteins from the contractile apparatus was studied. Vikhlyantsev et al (44) measured titin levels in muscle and myocardium samples of Mongolian gerbils exposed to a 12-day flight onboard the FOTON-M3 (Russia, 2007) satellite. An approximately 2-fold increase in the long-to-short titin isoforms ratio (N2BA/N2B) was observed in the postflight group of gerbils.…”