A non-catalytic function of the Src family tyrosine kinases controls prolactin-induced Jak2 signaling.
The cytokine prolactin (PRL) plays important roles in the proliferation and differentiation of the mammary gland and it has been implicated in tumorigenesis. The prolactin receptor (PRLR) is devoid of catalytic activity and its mitogenic response is controlled by cytoplasmic tyrosine kinases of the Src (SFK) and Jak families. How PRLR uses these kinases for signaling is not well understood. Previous studies indicated that PRLR-induced Jak2 activation does not require SFK catalytic activity in favor of separate signaling operating on this cellular response. Here we show that, nevertheless, PRLR requires Src-SH2 and -SH3 domains for Jak2 signaling. In W53 lymphoid cells, conditional expression of two c-Src non-catalytic mutants, either SrcK295M/Y527F or SrcK, whose SH3 and SH2 domains are exposed, controls Jak2/Stat5 activation by recruiting Jak2, avoiding its activation by endogenous active SFK. In contrast, the kinase inactive SrcK295M mutant, with inaccessible SH3 and SH2 domains, does not. Furthermore, all three mutants attenuate PRLR-induced Akt and p70S6K activation. Accordingly, PRLR-induced Jak2/Stat5 signaling is inhibited in MCF7 breast cancer cells by Src depletion, expression of SrcK295M/Y527F or active Src harboring an inactive SH2 (SrcR175L) or SH3 domain (SrcW118A). Finally, Jak2/Stat5 pathway is also reduced in Src-/- mice mammary glands. We thus conclude that, in addition to Akt and p70S6K, SFK regulate PRLR-induced Jak2 signaling through a kinase-independent mechanism.
García-Martínez
José Manuel
JM
Instituto de Investigaciones Biomédicas A. Sols (CSIC/UAM), Arturo Duperier 4, 28029 Madrid, Spain.
Calcabrini
Annarica
A
González
Lorena
L
Martín-Forero
Esther
E
Agulló-Ortuño
María Teresa
MT
Simon
Valérie
V
Watkin
Harriet
H
Anderson
Steve M
SM
Roche
Serge
S
Martín-Pérez
Jorge
J
D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D053614:Janus Kinase 2 / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D011388:Prolactin / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011981:Receptors, Prolactin / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D018909:src Homology Domains; D019061:src-Family Kinases
D011981:Receptors, Prolactin; D050799:STAT5 Transcription Factor; D011388:Prolactin; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D053614:Janus Kinase 2; D019061:src-Family Kinases; C000631346:CSK protein, human; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa