Rap1a null mice have altered myeloid cell functions suggesting distinct roles for the closely related Rap1a and 1b proteins.
The Ras-related GTPases Rap1a and 1b have been implicated in multiple biological events including cell adhesion, free radical production, and cancer. To gain a better understanding of Rap1 function in mammalian physiology, we deleted the Rap1a gene. Although loss of Rap1a expression did not initially affect mouse size or viability, upon backcross into C57BL/6J mice some Rap1a-/- embryos died in utero. T cell, B cell, or myeloid cell development was not disrupted in Rap1a-/- mice. However, macrophages from Rap1a null mice exhibited increased haptotaxis on fibronectin and vitronectin matrices that correlated with decreased adhesion. Chemotaxis of lymphoid and myeloid cells in response to CXCL12 or CCL21 was significantly reduced. In contrast, an increase in FcR-mediated phagocytosis was observed. Because Rap1a was previously copurified with the human neutrophil NADPH oxidase, we addressed whether GTPase loss affected superoxide production. Neutrophils from Rap1a-/- mice had reduced fMLP-stimulated superoxide production as well as a weaker initial response to phorbol ester. These results suggest that, despite 95% amino acid sequence identity, similar intracellular distribution, and broad tissue distribution, Rap1a and 1b are not functionally redundant but rather differentially regulate certain cellular events.
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202, USA.
Yu
Y
Li
Jingliang
J
Yan
Pradip
P
De
Hua-Chen
HC
Chang
Akira
A
Yamauchi
Kent W
KW
Christopherson
Nivanka C
NC
Paranavitana
Xiaodong
X
Peng
Chaekyun
C
Kim
Veerendra
V
Munugalavadla
Veerendra
V
Munugulavadla
Reuben
R
Kapur
Hanying
H
Chen
Weinian
W
Shou
James C
JC
Stone
Mark H
MH
Kaplan
Mary C
MC
Dinauer
Donald L
DL
Durden
Lawrence A
LA
Quilliam
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D054421:Chemokine CCL21 / Q000494:pharmacology; D054377:Chemokine CXCL12 / Q000494:pharmacology; D002633:Chemotaxis / Q000235:genetics*; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology; D051379:Mice; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000187:drug effects / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology; D010587:Phagocytosis; D010703:Phorbol Esters / Q000494:pharmacology; D016897:Respiratory Burst; D013481:Superoxides / Q000378:metabolism; D020668:rap GTP-Binding Proteins / Q000502:physiology*; D020827:rap1 GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*
D054421:Chemokine CCL21; D054377:Chemokine CXCL12; D010703:Phorbol Esters; D013481:Superoxides; C492136:Rap1b protein, mouse; D020668:rap GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins