Fiber-type-specific αB-crystallin distribution and its shifts with T₃and PTU treatments in rat hindlimb muscles

Abstract

Changes in alphaB-crystallin content in adult rat soleus and extensor digitorum longus (EDL) were examined after 8 wk of 3,5, 3'-triiodothyronine (T(3)) and propylthiouracil (PTU) treatments. Cellular distributions of alphaB-crystallin expression related to fiber type, and distribution shifts with these treatments were also examined in detail from the gray level of reactivity to specific anti-alphaB-crystallin antibody. alphaB-crystallin content in both soleus and EDL muscles was significantly decreased after T(3), and that in EDL was significantly increased over twofold after PTU treatment. In both control soleus and EDL muscles, the gray level of type I fibers was higher than that of type II fibers. alphaB-crystallin expression among type II subtypes was muscle specific; the order was type I > IIa > IIx > IIb in control EDL muscle and type IIx > or = IIa in soleus muscle. The relation was basically unchanged in both muscles after T(3) treatment and was, in particular, well maintained in EDL muscle. Under hypothyroidism conditions with PTU, the mean alphaB-crystallin levels of type IIa and IIx fibers were significantly lower than levels under control conditions. Thus the relation between fiber type and the expression manner of stress protein alphaB-crystallin is muscle specific and also is well regulated under thyroid hormone, especially in fast EDL muscle.

αB-Crystallin-coated MAP microtubule resists nocodazole and calcium-induced disassembly

“…Otherwise, it seems that the possible function additive above discussion might relate closely to a maintenance of tensegrity of cytoskeletons (Ingber, 1993) against long-lasting tonic contraction. Because all sHSPs are highly expressed in muscle cells, especially in heart (Dubin et al, 1989) and in slow skeletal muscle (fiber-type-dependent expression) (Atomi et al, 2000), the function of these tissues might be related to tonic contraction, to be maintained with endlessly energy-consuming fashion. In addition, a close correlation has been reported between oxidative metabolism and the expression level of αB-crystallin in various cells in rat tissues (Iwaki et al, 1990).…”

Multifunctional Roles of αB-Crystallin in Skeletal and Cardiac Muscle Homeostasis and Disease

“…All type 1 aerobic fi bers (slow-twitch) and about half of type 2 anaerobic fi bers (fast-twitch), corresponding to mostly type 2A fi bers, were positive for αB-crystallin, with more intense staining in type 1 fi bers. Additional studies confi rmed higher expression of αB-crystallin in slow-compared to fast-twitch fi bers (Golenhofen et al 2004 ;Atomi et al 2000 ). Variable expression in different types of skeletal muscle fi bers may account for specifi c fi ber-type degradation, but this would not account for the lack of cardiac involvement, since αB-crystallin levels are comparably high in the heart (Golenhofen et al 2004 ).…”

Gravitational Effects on Human Physiology

“…M-lines are largely composed of embryonic heart (EH)-myomesin in slow muscles, and M-proteins in fast muscles (Sjöström et al 1982;Schoenauer et al 2008). The protein turnover rate is higher in slow muscles due to higher rates of protein synthesis (Atomi et al 1991b) and higher chaperone contents have also been reported in slow muscle (Atomi et al 2000). 'B-crystallin is one of these chaperone proteins (Fujita et al 2004;Ohto-Fujita et al 2007) that is reported to be rich in the soleus muscle (Atomi et al 1991b;Koh and Escobedo 2004;Sakurai et al 2005).…”