Deletion of muscle GRP94 impairs both muscle and body growth by inhibiting local IGF production.
Insulin-like growth factors (IGFs) are critical for development and growth of skeletal muscles, but because several tissues produce IGFs, it is not clear which source is necessary or sufficient for muscle growth. Because it is critical for production of both IGF-I and IGF-II, we ablated glucose-regulated protein 94 (GRP94) in murine striated muscle to test the necessity of local IGFs for normal muscle growth. These mice exhibited smaller skeletal muscles with diminished IGF contents but with normal contractile function and no apparent endoplasmic reticulum stress response. This result shows that muscles rely on GRP94 primarily to support local production of IGFs, a pool that is necessary for normal muscle growth. In addition, body weights were ∼30% smaller than those of littermate controls, and circulating IGF-I also decreased significantly, yet glucose homeostasis was maintained with little disruption to the growth hormone pathway. The growth defect was complemented on administration of recombinant IGF-I. Thus, unlike liver production of IGF-I, muscle IGF-I is necessary not only locally but also globally for whole-body growth.
Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Elisabeth R
ER
Barton
SooHyun
S
Park
Jose K
JK
James
Catherine A
CA
Makarewich
Anastassios
A
Philippou
Davide
D
Eletto
Hanqin
H
Lei
Becky
B
Brisson
Olga
O
Ostrovsky
Zihai
Z
Li
Yair
Y
Argon
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002478:Cells, Cultured; D006128:Growth; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013002:Somatomedins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis
D001786:Blood Glucose; D008562:Membrane Glycoproteins; D013002:Somatomedins; C053387:endoplasmin