Titin‐cap associates with, and regulates secretion of, Myostatin

Abstract

Myostatin, a secreted growth factor, is a key negative regulator of skeletal muscle growth. To identify modifiers of Myostatin function, we screened for Myostatin interacting proteins. Using a yeast two-hybrid screen, we identified Titin-cap (T-cap) protein as interacting with Myostatin. T-cap is a sarcomeric protein that binds to the N-terminal domain of Titin and is a substrate of the titin kinase. Mammalian two-hybrid studies, in vitro binding assays and protein truncations in the yeast two-hybrid system verified the specific interaction between processed mature Myostatin and full-length T-cap. Analysis of protein-protein interaction using surface plasmon resonance (Biacore, Uppsala, Sweden) kinetics revealed a high affinity between Myostatin and T-cap with a KD of 40 nM. When T-cap was stably overexpressed in C(2)C(12) myoblasts, the rate of cell proliferation was significantly increased. Western analyses showed that production and processing of Myostatin were not altered in cells overexpressing T-cap, but an increase in the retention of mature Myostatin indicated that T-cap may block Myostatin secretion. Bioassay for Myostatin confirmed that conditioned media from myoblasts overexpressing T-cap contained lower levels of Myostatin. Given that Myostatin negatively regulates myoblast proliferation, the increase in proliferation observed in myoblasts overexpressing T-cap could thus be due to reduced Myostatin secretion. These results suggest that T-cap, by interacting with Myostatin, controls Myostatin secretion in myogenic precursor cells without affecting the processing step of precursor Myostatin.

Distinct roles for telethonin N‐versus C‐terminus in sarcomere assembly and maintenance

“…Therefore, titin must be rigidly and precisely anchored within the sarcomere, and this is accomplished in part by a small 19-kDa Z-disc protein called telethonin, also known as T-cap (Valle et al, 1997;Gregorio et al, 1998;Zou et al, 2003Zou et al, , 2006Pinotsis et al, 2006). In addition to binding titin, telethonin is also known to interact with other Z-disc proteins like FATZ , (MLP) muscle LIM-protein (Knöll et al, 2002), calsarcins 1-3 (Frey and Olson, 2002), minK, the potassium channel b subunit (Furukawa et al, 2001), and myostatin, a negative regulator of skeletal muscle growth (Nicholas et al, 2002). Incorporation of telethonin at the Z-disc via binding to titin and FATZ appears to be one of the last stages in maturation of the Z-disc (Wang et al, 2005).…”

Alpha-mangostin promotes myoblast differentiation by modulating the gene-expression profile in C2C12 cells

“…20) Titin-cap blocks myostatin secretion by interaction with myostatin. 21) Follistatin also antagonizes myostatin by direct protein interaction. 22) We confirmed the changes in expression of titin-cap and follistatin (Fig.…”

Growth Effect of Oncorhychus masou by Recombinant Myostatin Prodomain Proteins Derived from Fish

“…어류 myostatin은 포유 류와 달리 2가지의 isoform이 존재하며, 주로 골격근에서 발 현하는 포유류와는 달리 골격근을 포함한 거의 모든 조직에 서 발현되는 것으로 알려져 있다 [24,27,29] [22], follistatin related gene (FLRG) [9], growth and differentiation factor-associated serum protein-1 (GASP-1) [10], human small glutamine-rich tetratricopeptide repeat-containing protein (hSGT) [35], Titin-cap (T-cap) [23], myostatin prodomain [16] 등이 있으며 이러한 인자들은 활성 myostatin이 activin type Ⅱ 수용체와 결합을 하지 못하도록 하여 신호전달을 억 제하는 것으로 알려져 있다 [9,10,22,23,35]. 최근 myostatin prodomain을 이용한 활성 myostatin 억제에 관한 연구에 의 하면 무지개 송어 치어에 넙치유래 재조합 myostatin prodomain을 처리한 결과 최대 약 42% 무게 증가를 나타내었다 [15] (Fig.…”